How well you acclimatize can be largely genetic. Some people do it well, some people do it poorly. But you can help your body hit its max performance by doing what other people have suggested.
1) Drink, drink, drink, drink (water)
2) No booze
3) Eat, eat, eat - you need energy. I'm sure you're supposed to avoid fats or something, but the most important thing is that you choke down food like its your job. Especially if exercising.
4) Take it easy for a day or three every time you hit a new altitude above 9,000 feet.
5) Exercise with a heart-rate monitor. I've actually heard that the level of exertion which improves altitude performance is not balls-to-the-wall panting and wheezing, but rather extended time holding a pace where you can just barely hold a conversation.
Listen to your body like mad, everyone is different. I've seen folks that after a week at 10K+ cannot handle 15K without problems. I've seen other folks that after 2 days at 10K, head up to 17-20K without a care in the world.