As someone who has played several weeks now I thought I'd add a few lessons I learned the hard way. All this info is contained in the wiki, trainer website and these forums but people are reluctant to look for it. Here's a down and dirty summation.
1. You epically won at "MicroScrumpCorp WWII Ace Fighter Jockey I,II,and III" so you'll come here and own too. Totally wrong! Most of these guys have been here for years and your chances of upping a plane and killing someone right off the bat are very very low. Stick with it, even after the 2 week trial, it will eventually happen where you start getting kills.
2. The trainer website and training arena are your bestest friends. Use them!
3. Record every engagement to start and review the footage often! The things you did wrong usually are apparent on the films and will help you learn.
4. Research,research,research...knowledge is key. Know what your plane will do, and more importantly what it won't do.
5. Don't hop into the game the first day and start asking how to start your aircraft, where the fight is, or other assorted "I'm a new guy-please shoot me down" questions. Save those questions for your foray in the trainer arena.
6. This is a pretty close knit bunch, most don't want to talk to you at the beginning. They see hundreds and hundreds of people come and go but few that stay. Why waste time helping or even talking to someone who will be gone in 2 weeks? Would you? Training area will most certainly help you, that's the exception to this.
7. Don't attack bombers from the 6 o'clock position. You just spent forever and a day climbing to their altitude just to get chainsawed in half by tail guns cause you were stupid. (personal experience)
8. Know your role.... ok by now you know you suck at fighters, bombers and possibly tanks, maybe you should make troop runs. How about doing supps and listening to vox on what's going on. Man the ack guns or forward 5 inchers on CVs. If a huge furball breaks out over a base and you want to help, please do so but don't up a plane just to be shot down 17 seconds later when you can really be a killing machine in a Whirby.
9. PATIENCE! These guys didn't get this good in one day, and you won't either. Think "nose to the grindstone" here.
10. Enjoy the experience! From what I can tell, most of the damage models and flight characteristics are pretty close to the real thing. Envision yourself flying an airplane or driving a tank that was built by the lowest bidder or possibly forced labor. Said aircraft/tank was pretty much hand crafted, then shipped or flown thousands of miles just to be used as a weapon of war. After a few days of playing this simulation, it's amazes me that anyone, Axis or Allied, ever made it home from this conflict.
There are a ton more lessons but these are some of the main ones I have seen in my limited time here.