The training missions are almost useless. Don't sweat over them.
Your most important "learning" asset is the Academy at http://www.alleg-academy.org.
Other than that, practice ingame.
If you need to 'learn the controls' and get your key mappings set up right, log into an empty server or a newbie server. Do all your setup and initial key-learning there.
Once you have the hang of it, join a real game and fly for the commander of your choice. Remember: you're playing THEIR game, not yours!
--TE