Here's are a few links that I found with some great instructional info on kissing.
How to Kiss - Instructables - DIY, How To, lifehttp://www.instructables.com/id/How-to-French-Kiss/But I basically agree with the other posts on here. Relax and let it come naturally. The biggest way to screw up a kiss is to over think it. It really is a natural part of who we are as human.
Having said that, it never hurts to ask for feedback from the one you're kissing because everyone like to be kissed differently - some like it soft, some like it hard with a lot of tongue, and still others don't really like tongue at all...
So just practice, practice, practice and see what feels good to you.