Or alternatively make the potion so that it produces a minor/major/severe consequence on the imbiber of "extremely lucky", "things are just going my way", etc. That way if the PC wants to use it they can spend fate points, if the GM wants to compel it it's there. And by definition it can last a long time. Downside is that the character has less consequences that they can suck up from other sources.

Taken from the stories you could have it apply to any particular roll including those that aren't magic. I'm thinking of the non-magical times that a certain shadow helped Harry along. If I remember correctly there was discipline to control pain, a method to get out of the thorn manacles (athletics or endurance), translating ancient sumerian (scholarship) just to name a few... I would think that those examples would apply. Otherwise he would have got out of those situations using some other means...

Instead of applying an aspect via a manuever, why not just make an attack for consequence. Like an addictive saliva consequence. All the attack shifts could go towards a consequence that is something like "knocked out cold" or "throat slit", and compel the consequence as normal. Or tag for another attack.

But most of the surprise attacks we're talking about here are hand to hand which would probably involve a grapple result as well as a more specific attack. So the grapple could prevent the victim from alerting others while the results of the attack take effect. Why not do this as a grapple with weapon:+x added as well as any other tags, declarations, etc?

Given some situations that Harry got himself into, he collected magic energy into himself to use after a trapping circle cut off the ambient supply. Any thoughts on how to do this in the game?

And I had a secondary question: Harry fighting uberghouls and he's pretty much tapped out. Then asks "someone specific" to kiss him to get that extra boost of emotion to invigorate him to cast a really powerful shield spell. How would you explain that one mechanically in the game? Scene change perhaps?

I ran my first DF session a couple weeks back with my usual gaming group. The feedback was positive, but they came up with a couple good questions. Since we're usually using game systems with lots of situational modifiers like 'hiding in cover' and such, it took a little bit for them to catch on. The one question that popped that I didn't have a good answer to immediately was based on this situation: character is fighting in an alley, makes an appropriate assessment to find good cover (behind a car), goes to cover and stays there while bad guy unloads assault rifle for 3 turns. The first turn they tag the aspect and use it for free defense bonus, after that they need to use fate points to get the defense bonus... seemed a little strange since the cover didn't change, the guy with the gun didn't move, and they just cowered in fear.

So the question was why do I have to spend all those fate points if the situation didn't change and they didn't hit me the first time. I thought about it afterwards and came to the conclusion that the first tag could have gone into a block against the guy with the gun. And I thought since the block isn't dependent on anything except the car being there, then it shouldn't go away until the bad guy manuevers around it, gets some good shots through it, or the character rabbits for someplace new or does something to lose his 'in cover'.

That way they get the block as a freebie after initially putting it up until they do something that negates it. Like shooting back.