Good advice Zazen. I'd like to add a couple.
Park the FP or M16 on a refuel pad. It allows you to exit with a landing. If you run low on ammo, go to the driver position and wiggle the joystick (you don't have to start the engine).
But I like to sit next to the tower on fields that have the tower on a hill. This gives me a better view, shields my six, and makes me more visible. The later is good to encourage nme to attack you instead of the VH. The best way to kill a plane is when it's headed straight at you.
It's interesting how some players accuse you of gaming and bring up the old tired advice on upping during a vulch fest. I have often ended a vulch fest single handed with an Osty, allowing my countrymen to take off and defend. Now AH2 has made it much more difficult to hit an nme plane with a GV. And field guns are almost worthless. This strips our ability to defend bases, so IMO any advantage we can gain is worthy. Else, we may as well have one country and a bunch of undefended bases to attack, with lots of AI planes taking off to vulch.
One thing I've noticed in AH2 is a variance in the hit point on the 37mm cannon. Pick a target at a good distance and fire at it. Then compare where the hit sprites appear in relation to the cross hair (there's a lot of variance). Now try it in zoom mode and note if the sprites are in the same place. Try the same thing at different distances. I've found that in zoom the bullets hit below and to the left of the cross hair. And this varies with distance. Perhaps this can explain how a plane can fly directly at you and pass by without suffering a single hit. Either that or lag/rubber bullets. All is not fair for field defense.