Should you take birth control after you become sexually active or before?

Before, of course: If a couple waits until after they are sexually active to start a birth control method, they might have already gotten pregnant from the first sexual event. So, if planning to have sex, or planning to be in a position where sex might "spontaneously" happen, be sure to have condoms within reach... Or start birth control pills (or another method) a couple of months beforehand.