http://www.erowid.org/chemicals/mdma/mdma.shtml
http://www.pillreports.com

Read erowid to find out about it and check pill reports to check you're getting ok pills. Also try to get a pill testing kit if you're going to eat X.

A good tip is to eat 500mg of Vitamin C before, during and after to minimise the bad effects E has on your brain and to generally soften the blow.

Drink 500ml of water per hour of dancing.