1. Take a deep breath and relax.
2. Just be natural. Enjoy being with the person.
3. If you find at some point it's not natural and you don't enjoy being with them, move on. The earth will still keep spinning.
4. Don't go anywhere or do anything you are not comfortable with. Remember you have years ahead of you. You are always your own boss and can say no to anything.
5. Even if you did somehow eventually "mess it up," forgive yourself, maybe it wasn't actually meant to be. But if they can't live with small mistakes from you, you might be better off without them too.
6. Remember the other person probably has a few anxieties about things too and may not be that different from you.
7. Never sell yourself short. If he needs to put you down, you don't need him.
8. Be interested as well as interesting.
9. Read the Desiderata (short text poem, timeless wisdom, easy to find).
10. Have fun :-)