You can do some things to protect yourself from STDs, but keep in mind that not having sex or sexual relations (abstinence) is the only sure way to prevent STDs.
Use a latex condom every time you have sex.
Limit your number of sexual partners.
Have sex with only one person who's only having sex with you.
Choose your sex partners with care.
Get checked for STDs.
Don't use alcohol or drugs before you have sex. You may be less likely to use a condom if you're drunk or high.
Know the signs of STDs.