I tend to push towards concessions on lesser enemies instead of pointing out that they have less consequences...also when time is of the essence...

"You've made some pretty good arguments as to why the guy should leave the enemy and join you.  If it's cool he's going to concede and tell you that maybe his boss isn't looking after him properly, and he'll consider what you said.  If you want to win him over completely, it's going to take a few more minutes of conversation, and the biker gang is going to get further away from you"

"You've taken down three of the eight gang members... the rest are going to try to run, leaving their fallen buddies behind.  Is it cool if we call that a concession and go ahead and move towards interrogating the one dude you left alive?"

On the BBEG, I tend to actually have valid escape plans (insta-spell back into the nevernever is popular) to use instead of trying to rely on concessions.  So I approach the concession by giving the players something extra, like this: "Ok. here's the deal; the dude has a pretty reliable escape potion that will get him out of here.  We can roleplay that out and he'll likely do so successfully without giving anything away, or we can just say that he concedes here, using the potion but accidentally dropping a piece of paper as he tries to scramble for the potion."

That said, because i was trying to teach my group how THEY could use concessions, I used concessions for bad guys consistently, even when it could have ended in death.  The only time I didnt offer a concession was when the enemy was something unintelligent like zombies or w/e.

there is absolutely nothing in the rules that forbids creating a thaum. ritual that replaces your rapport skill with a magical skill of 9 (or 13, or whatever) until the next sunrise.  RAW, that's completely valid.

So is a spell that replaces your guns with a 9 for the same duration.

This is pretty much directly out of the Thaum. section of YS, and is allowed.  The complexity of the ritual is equal to the level you want to set the skill.  All thaumaturgy ends, unless you intentionally change duration by varying complexity, at the next sunrise.

So every morning any thaumaturgist could cook up a simple little ritual that gives him 5 alertness. (or any other skill).

Superior Senses (Biomancy)
Complexity 5
The character uses magic to heighten his own senses, fine-tuning them to perfection.  This lasts until the next sunrise.

If you're a high discipline person, you could easily dump 3 points of power into this spell every exchange and have it completed in 2 exchanges.  As the exchange time for thaumaturgy is NOT listed in the books but IS supposed to be longer than that of a combat round (as that is evocation's speed), I'd argue that any thaumaturge worth his salt could pull this off in 2 minutes.

Because this quickly turns into an alchemist with lore 5, item strength +5 (from foci and specializations), so the person now has access to on-the-fly spells that give them a rating of 10 in any skill they want, I -as a GM - began imposing a consequence for any spell that set your attribute over your normal maximum skill level for your refresh level.  I also ruled that all potions last at most one scene, and the default potion time is "a few moments".  Which is more generous than the novels, where potions tend to last what would be just a few combat rounds/exchanges.

An example of this from our game was:
Eagle Eye Potion, take 1 (potion strength 10)
Drinking this potion gives the character guns 10 for a few moments. After the potion wears off, the imbiber takes a mild consequence of "blurry vision".

Eagle Eye Potion, take 2 (potion strength 10)
Drinking this potion gives the character guns 5 and alertness 5 for a few moments.  No consequence is applied (neither skill went over the normal maximum of 5 for that character, he just made the potion effectively carry 2 spell effects, which is allowable)

---- Anyways, yes, you can totally use a spell to raise your rating in a skill to a level equal to the complexity of your spell.  Whether or not you can do this on the fly with soulfire (thaum at the speed of evocation) is up to your GM, as that issue hasnt been clarified (soulfire doesnt specifically say "at the speed of evocation", where every other sponsored magic says that. It has not been clarified if this was simply forgotten, or was not supposed to apply to soulfire... so it's debatable).

If you CAN use it on the fly, then you could model the character's CALM DOWN! action as raising your intimidation skill to the level of power you set the spell at, then making a normal intimidation attack. That attack would deal normal stress and cause consequences but would NOT specifically inhibit actions as you stated.  However, if someone got an aspect of "cowed" or the like, you could then, yes, invoke for effect (tagging the consequence for free, as you can do once with any consequence that you create), meaning that the bad guy either can't act but gains a Fate point, or can act but pays a fate point.

 

Side note:  There's some diminishing returns with having a high frequency on potions.  The combat advantage of a potion is not having to declare it beforehand and using the FP or lore roll (which you're likely to make, given that you need high lore anyways for crafting) to declare the potion on the spot.

That said, once the potion is declared, you're stuck with it for that session. So suddenly having 5 uses of "truth serum" (raises your empathy levels to new heights so you can tell when people lie) with you for that session may not be advantageous, as you're probably only going to need it the one time.

So an alchemist relying mainly on potions may be better off buying the refinement for extra slots, vs extra uses.

However, if you did have 5 uses, potions can be used by other people, so now one slot could potentially cover everyone in the group.

If you've got other enchanted items, and then a couple of potion slots, then the frequency boost for your items is great, and when you declare the potion just try to think of something that could be handy multiple times, or for more than one character.

This answer varies greatly according to:

1) How many players you have
   a) fewer players makes it easier to compel one repeatedly and stay with the story line
   b) a bigger group seems to benefit from situational compels; asking "who has an aspect that they think would compel them to [save the princess/slay the dragon/do X] here?" is a good strategy.
   c) Bigger groups make personal agendas like "looking for my lost sister" really hard to compel while keeping the story universal.
   d) 5 players means you're keeping up with 35 PC aspects.  8 players means you have 56!  You're just NOT getting to all of those.

2) How well the characters blend together / were designed to mesh at character creation
    a) IF your nerdy scientist type has all his aspects about investigating things, and the werewolf is all about hitting things, then some scenes are only going to hit one person.  If the nerd had an aspect of "help the werewolf", now he gets compelled in all the fight scenes.
   b) IF you have players with completely disparate main agendas, it's harder to compel them at the same time.  IF those last two phases reflect a bond between the characters, then it's easy to compel one character onto the other's agenda. IF one has aspects about being a do-gooder and the other about being selfish, it can be difficult (but fun) to compel both simultaneously.

3) If you write scenes around the characters' aspects
   a) several blogs (rick neal, ect) suggest planning scenes by linking them to character aspects.  The simplest (I really pared this down from the blog) version is to put all the PC aspects onto scraps of paper, then draw a few from a hat as you script each scene and specifically design elements in the scene for that aspect compel. Then, WRITE THAT DOWN so you remember to compel.
  b) by choosing aspects, the players have told you the kind of game they want to play. IF you write a scene that includes one of each character's aspects (easy with a group of 4 or less, again, big groups complicate this), then you'll usually find that you end up compelling much more than just the one aspect, because you're hitting on what the players wrote their character around.

4) How readily your characters self compel
  a) this is pretty obvious, but again, way more important in a bigger group.  Training new players to this is key; after a while my players would choose to fail in a scene to earn fate points.  "Hey, it would be really inconvenient for me if I couldn't get this info out of his computer. Can I have a compel on my high aspect [wizard]".

5) How easy the aspects are to compel.
  a) also pretty obvious, but if you write your aspects in latin or haikus or whatever, and it's not really obvious what that aspect is for (yes, even if we had a conversation about what you wanted it to mean), then it's damn hard for me to compel.  Really good blog advice on this one, too (can't remember if this was Rob or Rick), about having the aspects be kind of like catch-phrases for the character.  IF the character would say it, or if it would apply to the character, then it's a compel.  (I think this was Rob. He's at http://rdonoghue.blogspot.com).   
  b) equally, the book and every blog give a ton of advice on making compels both positive and negative, so you can both compel it and use it.  Here's my own personal take on that:
   For every point of available refresh you have, you can have one completely positive aspect, OR one obscure/ mostly irrelevant aspect (looking for my lost sister, in a large group).  Meaning, a wizard with -1 adjusted refresh really needs 6 out of his 7 aspects to be things that I can compel.  Meanwhile, the pure mortal with an adjusted refresh of 4 can really afford to take 4 completely positive aspects.  He's going to be starting battles with plenty of FP, and refreshing each game easily. If his other 3 aspects are really broad and focused around his character concept, he'll earn those easy enough.  He really needs to focus on outlets, though, making sure he can spend those points readily.
  Never, ever, ever take a completely NEGATIVE aspect.  It's your job as a player to figure out how to use your weaknesses to your advantage.  "Blind" is a horrible aspect.  "Keen-eared, blind old seer archetype" is immensely useful.
  c) if the players wrote their aspects to cover all three categories of combat (physical/mental/social), the aspects can be useful in most situations.  IF they wrote all physical, then it's hard to compel them in a social scene. If they wrote one aspect for each type, they can run out of ways to compel in each scene.  So I try to encourage players, for EACH aspect, to list how it would be used both positively and negatively in at least two out of the three types of combat.    For instance, I had a player with the ultra-mature aspect of "big boobs!", but actually this ends up being pretty easy to compel or invoke in all three types.

Wow, this was long. Hope it helped!

We use a very, very, very broad interpretation of this:

Are they inhuman? Then magical affinity counts.
Are they human with a Lore score above zero?  Then magical affinity counts.  Absolutely anyone with any understanding of magic recognizes that this person is marked somehow, but maybe doesn't recognize the mark itself.  That's why the bonus counts even at that level: you know the person is connected somehow, so you play it safer (they get the bonus).

What I'm trying to figure out is how to handle this lower level hexing.  I don't want them to have their cars break down everytime they get in them, for example.  And the shaman, at least, has a 'beat up old chevy' of some unspecified year that he drives specifically for that purpose.  And clearly, they must still be able to at least use computers some of the time.  But I'm trying to figure out how to model a highly increased chance of hardware and software problems resulting from their magic in a story telling way.  I don't intend it to be something that really screws up their lives, more of a "you've noticed that lately, your computer crashes.  A lot."  and only really treat it as a compel if it's something like "Sheridan, your gun jams on the second shot" as a side effect of the evoker sorcereress throwing around blasts of power.

If you just want it for story effect, then whenever they roll badly on a roll - say, like, failing a contacts roll - just blame it on a hex. "You knew just the guy to call, but when you went to call him your entire phone list in your cell phone appeared to be missing." miss a drive roll by one? "For a moment, the car just completely stalls, you lose power steering, the lights go out.  You realize your heart is racing and that your emotions may be causing your magic to make the car go wonky".

Basically, you aren't imposing ANY penalty mechanically... you're just blaming the players' bad rolls on a story aspect.

This can be really cool because the driver could say, "Ok, I want to take a deep breathe and really focus" as a discipline manuever to assist the next drive roll. 

Make/use whatever you want, adjust the stats so that it's primary offense and defense (athletics, weapon, w/e) are on par with the average for your party, and don't run it with full consequences. (Read over the section on opponent importance to the story, where it talks about what consequences an enemy might take at what levels).

In high powered campaigns, you can actually blow through the entire consequence scale pretty quickly.  When someone has a 14 targeting roll, exceeds their opponent's defense by 10-ish, and then rolls like 24 damage into stress - well consequence boxes kind of go poof.

But when you're doing your best to pump out a couple of spells with a targeting roll that might not even hit, the difference between an opponent with one mild consequence or an opponent with even just one mild and one moderate can literally swing the fight.

The only thing you really need to avoid is something that characters might not have access to defeating, like ghosts, creatures weak only to earth magic (none in the books, but still, it'd be tough), and so on.

Also, if they are having a really tough time, then try running a few non-combat scenes where their aspects can earn them some fate points before a battle. Most wizards go into a battle with few fate points, and a higher level wizard makes up for this by defaulting to magical defenses (the standard one enchanted item block, one enchanted item armor set up)... but at lower refresh, your spellcasters are probably burning refresh and focus items just to do their primary function at a decent capacity. So they are truly glass cannons - probably really no good defense skill, no fate points, and no magic protection.  Walking into a fight with even 2 more fate points could swing the battle for them.