actually you could start right here! just do a search for "thinner ratio" or "which paint is best" and you will come up with tins of posts on it.. I know just in the last month or so the subject has been breached at least 7 or 8 times...
techniques you can read about here, but if you can find you a book like the two that were mentioned it would help, or go to
http://www.testors.com/hobbyist_guides.asp and check out the pdf on airbrushing.. actually all of the guides are decent on that site... can get a lot of tips about modeling as a whole!
Good luck to you! Best thing to do is if you have an old or cheap model practice!!! just play around and get used to holding the airbrush....