It is important to stress that the most important part is to overcome the critical period - until the body accommodates to asexual life, and then it will take no more effort. If you worry a sore all the time, it would never heal. If you leave it alone, it will soon be history. This is a physiological feature - the less sex you have, the less you want it (though this takes time to work). It is important, however, to be honest to yourself and not to feed lust with fantasies.
The following recommendations can be given:
Psychological state
First, make a clear decision, not something like "no partner right now, so let's be asexual for a while" - this would give opposite results. Understand all drawbacks and troubles related to sex. It's a good idea to write down your favorite reasons: re-reading it in times of temptation can be quite effective. Also, participating in an antisexual newsgroup has therapeutic value ;)
Next, idleness is a sin-catalyst. Your mind must be kept busy, which does not mean solving equations all the time, but don't just sit around bored. Avoid temptation such as watching sexually arousing movies or magazines. If yet bad thoughts occur, switch to something that will totally occupy your mind. Or, if this is too hard to do, try the opposite approach: recreate the scene that aroused you in your mind again and again, until the excitement disappears. Like with words losing their meaning from monotonous repetition, it kills the urge. (Of course, you must not masturbate when using this method. On the contrary, try giving your body mental 'orders' to calm down, and imagine it doing so. Remember: the body has no will of its own, all depends on your mind.
Relationships with members of opposite sex are not contraindicated, but if you are susceptible to romantic motives, try to avoid situations where your communication is mostly limited to one person. See more on this topic in the article "Prophylaxis and cure of love."
Daily routine
Do not sleep too much; 6 hours should be enough. If you lie down tired and flake out immediately, and get up as soon as you are awake, stupid thoughts will have much less chance to haunt you. Avoid using too warm blankets or otherwise overheating the groin. Certainly, you should never expose it to excessive cold as well, since it's harmful. Some asexuals recommend sleeping on the left side, although in general the most physiologic way to sleep is periodically turning from side to side. It is advisable to learn to control your mind while sleeping, and drive off lusty thoughts on first sight. Another good thing to do is going to bed and getting up early - before dawn, it you can. Physical exercises and cold or contrast shower are also good, both for celibacy and general health.
Food
Vegetarianism helps greatly, though it is not absolutely necessary. Among the foods that stimulate sexuality are: coffee, chocolate, honey, walnuts, yolks, hot spices, onions, moderate doses of alcohol. This does not mean, however, that those are completely prohibited - but beware.
On the other hand, drinking hypericum tea benefits both celibacy and health in general.