ASM always off, tsc off for lower power cars and a 1 for higher power; assists in standing starts, but low enough to allow wheelspin for drifting the corners (which i always do). but, me being who i am, i automatically assume that the game knows my preference and just defaults it off, so i often enter races finding that my car is acting like a bag of potatoes on a soapy kitchen floor...ok, really bad analogy, but i try sending something sideways into a corner, and what do you know...handles like mud. if anything, ASM would only ever be useful for me in removing understeer, but moot as i tune cars with understeer to make them more loose.
in the same manner, i have never chassy refreshed or rollcaged a used car; i like 'em with their quirks.