Ecstacy is a brilliant experience. I rate it as one of the most eye opening physical things that I've ever done, alongside travelling, having sex and discovering foreign cusine. That said;
1) Don't do it if you are prone to depression. It takes a week or two until you will feel totally chipper again. My theory is it takes the edge of your natural serotonin levels for a while, so you don't get the natural 'sunny afternoon' highs for a little while.
2) Do it at home with people that you like. People always seem to do it in clubs and dance, don't know why, it's more fun getting loved up with your mates.
3) Don't do it if you have an addictive personality. Ecstacy is a wonderful experience, it can make you think, 'so, this is what I want from life, to be like this', obviously if you get addicted to things and know that you sometimes have a problem seeing the wood from the trees, E isn't for you. A good test is, 'would I easily get addicted to cigarettes?' If the answer's yes, don't do E.
4) Don't do it if you want to have sex. It makes you totally impotent. All you'll want to do is cuddle.