My tip for making a girl cum is keep a constant pace and never rush.
No matter what you do, where you kiss, where you lick, go slow. Then listen for changes in breathing, moans etc. Once you find the places/areas that get her going, stay there. But always stay at a constant pace. I do this to their whole body as different girls have different sensitive areas. Seems to work.

I also encourage them to tell me what they like - makes it a hell of a lot easier.