One thing to remember, I think, is that magic (no, all actions, but with magic it is even more complex, I think) is all about intent. You do not have a spellbook like in most other games, but a set of tools to push your intent into a form on the fly.
For example:
If you want to attack with fire, that is pretty straight forward: aim and shoot.
If you want to put up a block, you need to get a little creative. Maybe you are laying down cover fire, so the other guy does not get a chance to attack you.
Story wise, you are doing the same thing both times: throwing fireballs. Mechanically though, one is an attack, the other one is created as a block (you could do the same thing with guns, btw.). A maneuver can be done the same way, because a fireball is also really good at putting the "on fire" aspect on things. Although a block like the one described above is probably going to put the "on fire" aspect on the scene without an extra maneuver.
Remind your players of that, or they are probably only going to use their rote spells, because they think that is their "spellbook". Get them to think about what they want to accomplish with their action, not what spell they want to use.
