Do these in any order you'd like, based on the enthusiasm of the moment.
- Define overall look & feel. By at least step #4, you should have a Relationship Map; this is all part of Versatile Preparation.
- Define look & feel for sorcerous rituals. Everyone should have a solid image of what their character really did to bind that demon they have.
- Have a neat list of descriptors to choose from that fits very well with both #1 and #2, and don't forget Cover.
The 'default' descriptors work reasonably well for a 'standard' or 'starter' Sorcerer game, but a good, evocative list of descriptors goes almost as far as a good Setting description to really spark players' imaginations -- a good list of descriptors will start giving people ideas for different characters almost immediately.
- Define look & feel for demons (how they act, how you'll play them, what kinds of awful things happen, etc); this doesn't have to be all that strong among the players, but you as GM should be champing at the bit to play demons as NPCs.
- Consider what you, as GM, will levy Humanity checks and award Humanity gain rolls for. Write these things down in a list. Give an example or two. Consider player feedback and input, and implement if it works for you and the group. It's not supposed to be a big debate.
- Make sure the Kickers are inspiring to you as GM.'
A Caution regarding the PC's Demons
The simple fact is that if the sorcerer doesn't have a desire or need to have a demon, then he simply banishes it and ceases to be a sorcerer. Game over. To make play work, the Sorcerer has to have a reason to have the demons he has.
This is what drives play - it's not about the cool powers, but why the sorcerer needs them. This sets up the dysfunctional relationship between the demons and sorcerer, all in relation to the humanity mechanic. Without the sorcerer's need, there's never any choices for him to make relative to humanity, and the game falls down.
Not giving a sorcerer a need for their demon in Sorcerer is like not giving a D&D character a class.