Thought I would share this tip, as it has worked with pretty much every girl I've had sex with.

Make sure shes laying down, and you're on top, missionary.
Hold her legs up, get them on your shoulders, put them in front of you and put them together, so her legs are in the air closed together.

Then keep fucking her, and this just seems to hit the spot EVERY TIME and they orgasm quite quickly.

Kinda like this: Deep Impact | SexInfo101.com

But hold her legs together!!