If there's air left at the end of the condom, it also increases the likelihood of breaking, says Rena McDaniel, M. The only surefire way to prevent contracting an STI is complete abstinence, but let's be honest, that's not always realistic, so condoms are the next best thing. Though your partner may have convinced himself that he's a Magnum-only type of guy, if he's not, speak up. Water-based lubricants are best with latex condoms.