Step 1. Do a one shot with throw away characters so players can get used to the aspect driven nature of the game.
Step 2. In that one shot, try to feature diverse pre-gens, I recommend Feet Wet characters just because the pre-gens are not that hard to make. I would just provide High Concept, Trouble, the first two phase aspects, Great skill, and 2 Good skills (this implies the 4/3/2/1 skill array). Then provide a mix of pure mortals and minor supernatural characters.
Step 2b. Try to ask the players to come up with an answer to some sort of question to help generate a 3rd phase aspect. Something like "You were in [this situation]... How did you get through it and what impact did it make on your life?"
Step 3. Try to feature scenes for all types of scenes and conflicts:
a. Social Conflict.
b. Investigative/Research Scene.
c. Usage of extended skills (like a chase scene).
d. Contacts (could be used to lead into said Social Conflict).
e. Physical Conflict finale. You don't even need to plan other physical conflicts, just make sure any social scene has the potential to go physical (so have those nameless guys ready), I guarantee that players can always find a way to turn a peaceful tea party into a bar fight.
f. Try to feature at least one or two compels as well as aspects. Aspects are the most important thing. This whole game is about aspects. Every scene should have at least one scene aspect.
Don't worry about mental conflict yet, except to explain that mental attacks represents having your mind bent.
At least half of this game is about accepting compels and spending fate points to invoke aspects.
The only reason for starting low powered is if it is pre-gens, it is a LOT less effort to pick 4 refresh of stuff, 4 aspects, and 3 skills than to make fully fleshed out Submerged characters for someone else to us. In my one-shot game at DresdeCon, I took this "Amateur Stunt Driver" and made it mine (James "Jimmy" Kloughn driving around in a P.O.S. Miata that has "Klown Car" spray painted on the hood). If the GM had selected all 7 aspects and all 10 skills, I am not sure if that would've happened.
Another reason is that it is easy to convince players to abandon (or adjust) a Feet Wet pre-gen for a Submerged character they design themselves. Although, I wouldn't mind redoing Jimmy Kloughn as any power level, it was just a really fun concept.
Recommend to players try to avoid writing down all of their extra skills until they use them. I know I was having a lot of buyers remorse feelings about picking Guns, Weapons, and/or Fists. And it just looks bad to see someone erasing and rewriting stuff on their character sheet (even if they haven't actually used those skills yet).
Another thing is that if you type up and print sheets, don't fill in the stress tracks entirely, maybe block off the right 5 boxes on a pure mortal (who doesn't have Endurance Good or Great), but leave 3 and 4 on each track open in case someone picks a track effecting skill of Fair or Average.