Well, if you want her to be pleased.. One thing you can do is this.
When you feel like you're getting closer to coming, pull out. Start pleasing her. Rub, kiss, tease places. Spend time on her. It'll help her get worked up which results in her coming. A lot of women it takes over 20 minutes of just foreplay before she is even close to coming. Everything has to be arroused for full pleasure to set it. Also, knowing the feeling of when you are close will help you hold back from coming so quick.
When you go back in, go slow, try different positions. Or even let her be on top so she can control her orgasm herself. If you have to, when she's on top and you feel like you're going to come.. Put some glow stars on the ceiling and count them lol (seriously though, my bf did that and it worked). It'll help distract you which in return, you'll have longer sex. As for what to do when she's almost there.. Keep up the same thing you're doing. If you change it up real quick, she could lose her orgasm.
And remember to wear a condom. =)