Okay guys, i have a question for you..what do YOU do to delay cumming during sex/love making?

Okay, im young (16) and my GF is 17. we have sex, and i can only last 5-15 min (15 once in a blue moon) but im wondering what you do to delay or just not *** while having sex..i got a guide for free on the internet but i wanna hear from real guys what you do..id love to please my GF alot more by lasting longer, its her satifaction i care about (: witch might be bad by the pressure im putting on myself..but i just wanna hear some tips/pointers you guys do to last longer. thanks (;