Yes, there are a lot of them, but they all come down to the same thing - basically knowing to block your orgasms.

While masturbating, bring yourself close as you can to an orgasm as you can without ejaculating then stop for a minute and start over. After you get enough practice in being able to block your orgasms 5-6 times in a row, try doing the same while your girlfriend's  giving you a hand \ blow job. The while having sex.

Also, a nice thing would be to just very your sex life a little bit, have sex in penetration, stop and make out, or go down on her while you take a break and then go back into penetration. You'll both have more fun.