I use the following points to get and hold a good head on my beers:
1) Rinse/clean the beer glasses in hot water only - no detergent. Detergent destroys head! If the glasses have been washed with detergent, rinse 3 times in hot water and this should alleviate the problem.
2) Keep the glasses cold, I just have a few in the fridge or whack one in the freezer for 10 minutes before pouring the beer.
3) Try an all-malt brew! These hold head [almost] no matter what in my experience.
4) Let the beer age a bit, 4 weeks and over is best. This will give better head retention and formation - 'young' beers generally just don't hold or form a good head.
5) Keep your beer quite cold, as this aids head retention as well. Only remove from the fridge just as you intend to pour it. Kind of goes without saying, but doesn't hurt to put it here.
There we go, you should be pouring a nicely headed beer in no time! :chug: