It is important to distinguish between birth control and prevention of STDs. While birth control pills and IUDs help prevent pregnancy, neither measure offers any worthwhile protection against disease.
Practicing "safer sex" is the most reliable way for sexually active people to protect themselves against STDs. Using a latex condom with a contraceptive foam or jelly is an excellent option. (Women can use a female condom as well.) The chemical in the foam or jelly kills some infectious microorganisms along with the sperm. (Warning: People who reach for a tube of contraceptive jelly during sex should make sure they do not accidentally grab a tube of simple lubricating jelly, which has no sperm- or germ-killing ingredients.) It's also wise to think about a partner's sexual history, and avoid intimate contact with people at high risk of infection, such as those with multiple sexual partners.
People who even suspect they might have acquired a sexually transmitted disease should stop having sex until they consult a doctor and find out for sure. If test results show an infection, it is essential to notify all sexual partners so they can be tested, too. It is vitally important to follow the treatment exactly as prescribed and to abstain from sexual contact until receiving a clean bill of health.
How Sexually Transmitted Disease Is NOT Spread
In most cases, people do NOT pick up sexually transmitted diseases from doorknobs, toilet seats, or towels. That's because the microorganisms that cause STDs thrive in a warm, moist environment such as the mucous membranes of the genitals or the mouth. Many of these organisms die soon after being exposed to dry air. (The virulent hepatitis B virus is a notable exception.)