That means staying monogamous, if you're already monogamous. It means being careful and smart, if you're not. Remember to use a condom every time you make love. Staying STD-free can be as simple as that. In fact, it's a game you don't even have to play at all.
Prevention is better than treatment, and caution is better than cure.
Most STD's fall into one of two groups. Gonorrhea is a classic example. But blisters and drips alone do not a diagnosis make. Chancroid, for example, is often misdiagnosed as syphilis, while chlamydia can cause gonorrhea-like symptoms. And other STD's produce no symptoms at all.