Abstinence is the best way to prevent all sexually transmitted diseases. Abstinence from oral and genital (vaginal, anal) sex is the 100% surest way to prevent a sexually transmitted disease.
Try to avoid any type of sexual contact until you are ready and in a mutually monogamous relationship.
If you do decide to have sexual contact, it is suggested that:
Go get tested regularly, like once a year by a doctor or at a clinic. A regular exam by a doctor or nurse that includes testing for sexually transmitted disease should be done at least one a year.