Hiya.. coupla tips that I use to do decent planes (or anything else for that matter) in 3d:
1) get a good 3-view ..side, top, and front are minimum.. bottom view if you're gonna model doors and gear accurately.
2) Build a plastic model of it .. a 3d shape really answers a lot of questions: ie: just how the Mustang canopy fits the fuselage that a 3-view doesn't show.
3) scan the 3-views in and use 'em to make a line shape template for top, side, and front that you can build over the top of.
From there you just have to go for it. Your first iterations will be high poly count .. as you get better at it you will get more effective.
Don't be afraid to select a set of faces, hide the rest, and work a specific detail until it looks right.. or even detach 'em and work 'em as a seperate object until you're satisfied. (wing-fuse joins f'rinstance)
A good model is only 30 percent of the total.. the rest of it is texture mapping and lighting (or environment).
For mapping .. gotta have reference.. attention to detail, know how things 'look' ..especially a plane that's been on open field operations for several months. They aint museum peices :)
-GE (late of Air Warrior, at Papyrus Racing now.. and otw to Falcon 5 in the near future :)