When?
Don't do this on your first date. Try to find out the accurate moment.
This depend on many factors - your and her personality, and many others.

First of all:
Make sure that brush your teeth.If you are a smoker don't smoke before your date.There is nothing worse than kissing her with bad breath.

Your lips need to be slightly moist.

It's very important to make sure that there are no other people.

The best moment of your first kiss is at the end of your date.You need to make sure is she ready for this.So don't plan to kiss her in advance.

What to do after first kiss:

This will be very intensive moment for you and for her so when you finish just look at her eyes, say "buy" and leave her alone.