As far as performance goes, I wouldn't worry about it. Sex isn't that hard and you figure it out pretty fast.

I'm not a sex expert but I do have some words of advise.

1. Make sure you are clean. If your smelling no so fresh it is a turnoff for most people.
2. Make sure your nails are trimmed. Nothing kills a mood faster than when things are heated and you put your hand down her pants, only to scratch her cliterous.
3. If you find yourself in the position of giving oral sex and have no idea what to do. Find her cliterousnand lick the alphabet. It sounds silly, but it works.
4.Listen to her. That is a good indication if your doing things right. If she starts breathing deeper, and maybe clinching up a bit then she is feeling good. If your lucky she will tell you what she wants and you don't have to do any trial and error.
5. Dont try to just stick it in. If she isn't excited then there will be too much friction to penetrate. Do some foreplay and give her time to get ready. The vagina releases lubricant when she is excited to aid in penetration, as well as widening up some to allow for penetration. Much like an erection you can't really control it and it happens when excited.

Don't worry too much about it and get yourself worked up. If you are not great the first time it isn't really a big deal. It takes people a little while to get to know each other sexually and what gets them off. Best of luck to you.