It's all about your mindset when you have sex. Now you have your mind an trying to last longer instead of just enjoying it. If you can manage to release your feelings and just have a good time, you'll definately do a bit better. Also, don't go full speed from the start, you have to pace yourself.
Another way i've read about is to let the female be on top when you are copulating. This relaxes you leg muscles, and you basically don't have to do anything, and it allows you to use your hands to stimulate her.
Also, if you can, try to masturbate about an hour before you have sex. You'll last alot longer.
If none of this works for you, just don't think about sex at all, and do some math in your head. Sometimes I find I have to resort to this. I just do powers of 5 as high as I can go. If you know that she is close to orgasm, or if she tells you she is, get your mind back onto the sex. If you get good at the timing and you have a bit of luck, sometimes you can have simultaneous orgasms. ^-^'