Use a latex condom. Proper condom use helps protect you and your partner from infection with STDs. Avoid risky sex practices. Sexual acts that tear or break the skin carry a higher risk of STDs. Even small cuts that don't bleed let germs in and out.
Anal sex poses a high risk because tissues in the rectum break easily.
Using birth control when you have sex is the best way to prevent unwanted pregnancy. If you have sex without birth control, though, you can use emergency contraception. It is simple and safe. It can greatly reduce the chance of pregnancy after unprotected sex. Call your doctor right away if you've had unprotected sex and don't want to become pregnant.