Only way to do it is to just take the plunge; you're going to be nervous, you're going to get shot at and you're probably gonna do stupid things that wreck your plane. But WOW is it worth it!
I still consider myself a rookie and still get nervous at times, but how awesome is a sim that can actually play with your nerves like that?
Find a good server, cough*ATAG*cough, and get a feel for the way things work; hopping on Teamspeak and communicating with your teammates will also help as most of the time nearby teammates are more than happy to assist you if you're in trouble.
Start off with realistic expectations and never allow yourself to get discouraged, attack some AI bombers until you develop your tactics and once you get more confident you can start to be a little more daring. I have been flying on ATAG for a month or so now and I am yet to win a 1-1 dogfight, but I sure as heck won't stop trying!
Some of the best pilots around are on ATAG and they're all incredibly friendly. Sure, going up against great pilots can be difficult, but the way I see it is; if you want to be good at something, you have to learn from (read: get owned by) the greats.
