I find that when it comes to sex, the biggest variation in girls is their ability to give a good blowjob. Any girl can lie on her back and spread her legs, and any girl can get on her knees to be fucked doggie style, that doesn't take too much talent. The real judge of a girls skills in the realm of sex is the blowjob. Thats where the girl either proves she's a champion in bed or not.
I've found girls range quite a bit in this category. At low end you'll find girls with no skills who demonstrate their lack of ability by their obvious reluctance to even give a blowjob. They're probably only doing it because you're their boyfriend and they want to please you. They usually try to just lick the cock, and will barely put it in their mouth for a half-hearted effort at sucking it. The whole charade lasts about 1-2 minutes and then she stops. Forget about cumming in their mouth or on their face, they think thats disgusting and will probably puke if you do.
At the high end, you find the porn star blowjob. Every guys fantasy because pornstars do it right (thats probably why they're pornstars). They take your cock in their mouth enthusiastically, sucking hard and deep throating it as much as they can handle. At the same time, they vigorously stroke your cock whilst sucking. When it comes time to cum, they will open wide and beg you to cum in their mouth. They swallow everytime, smile, and then tell you how much they like giving you blowjobs.
So here is my message to all the girls out there. If you want to be better in bed, go rent some porn and take notes on their blowjob techniques. Because the only thing worse than giving a bad blowjob is getting a bad blowjob.