Having just run Dresden Files RPG at a convention, here are my suggestions.
Have handouts for the players giving a (brief) outline of the FATE system covering the following points:
Skills and difficulties
Aspects and Fate points
How to perform actions/checks
Explanation of Mortal Stunts and Supernatural Powers
I found that I could generally explain how to play the Dresden Files RPG in just a few minutes, as the basic rules are easy and intuitive.
I would also recommend providing Pre-Gen characters, but as others have suggested, leave some areas blank for the players themselves to finish and also customize. This lets the players have much of the work of character creation done for them, yet still give them some room to add their own 'flavor' to the character, and it will also allow the player to fit the character into whatever their concept of the character should be.
For the Pre-Gens here are my recommendations:
1. Provide the High Concept, Trouble, Background and Rising Action aspects, but leave the First Story aspects empty, and have them filled in during game play.
2. Chose the skill tree to use, but leave some slots open for players to select (or rearrange) skills. In other words, a Feet in the Water character (20 Skill pts, max of Great) can have 2@ each of Great, Good, Fair and Average, and you might only fill in 1 each of the Great, Good, Fair and Average with the slots left empty for the player to choose.
3. Leave at least half the Refresh open for the Player to choose on their own. This is where a good deal of the favour of a character can come from. Additionally, you might have players that really want to/not want to play casters. Leaving several Refresh open allows the players to choose what to do there.
As an example, I had a pair of one-shots which I ran which took place at the Grand Opening of a Harry Potter-themed cafe & bookshop called the Leaky Cauldron. Running with the Harry Potter theme, the aspects for the characters as well as some of the skills were all based off some of the characters from the books or movies. By allowing a fair amount of customization for the players, I ran the same thing for two completely different groups and entirely different outcomes.