Here are some good guidelines:
for injecting - 22g, 23g, 25g - for oil-based steroids, 27g, 29g - for insulin, HCG, HGH, and some water-based steroids. 21g-25g for some lower quality types of winny or suspension, higher quality versions can use a smaller needle generally.
22g and 23g are fine for glutes and quads. 25g is preferred for the smaller muscles such as delts, biceps, triceps, etc.
Most people can get by with a 1" needle, but if you have a higher percentage of bodyfat or are just plain big you should use a 1.5" needle to insure that you get deep into the muscle. You should only use a 1.5" needle for glutes, or if you have huge quads. For smaller muscle groups, 1" is the most common, although some people like to use a 5/8".