Adding to good advice from D1visor...
Pressures are one of the most important thing for drifting. It really depends on car and weather but in general you want to have maximum possible grip on front and either something stable at the rear for high power/drift version cars or a bad grip for stuff that don't want to switch ends on power.
For front tyres, if you are drifting with semislicks (default tyre) you want to give 2-3 psi more. If If you pick street rubber and it's not default for that car 4-5 psi is advisable. I'd recommend against 90's slicks because they offer similar grip as streets but are less stable thermally.
For rear if it's something like E30Drift, you want about 20-22 psi so that as you heat the tyres up the grip >range< the tyres will go through will be smaller, giving you more stable platform to drift. For stock AC cars I usually use from 18 (if the car cooks the tyres like a good oven) to 25 psi (if the tyres barely overheat).
You can also try using 40+ psi rear to starve it for grip but that will switch the rubber for butter after it heats up and car will become harder to control, even if it's a dedicated drift machine.
Lastly, when trying to setup any car for drift, always try to first give front tyres as much grip as possible and then move to reducing rear grip (like zeroing camber) if it's not enough.
Even stuff like Lotus Elise SC drifts well with optimized front grip, while it's a pig to drift if you focus on taking it away from the rear.
(An exception to the above would be increasing power differential which is nice overall, but it's rarely possible on stock street cars.)
Bad that some picture links removed: http://www.racedepartment.com/threads/assetto-corsa-car-setup-guides.99049/ Hope someone will update it in future.
