1- Tree clusters to hide (and protect) yourself from attacks (I managed to survive a dozen bomb drops in a troop loaded M3 this way once it was pathetic). If you see some blue sky, you are not hidden enough. You risk finding yourself upside down easily though so be careful hitting those bushes!
2- Terrain elevation. Stay on the edge of descending slopes. And move on the down slope if a bomb drop is imminent. Bomb blast don't cause damage if they hit a bit higher than your tank or are obstructed by terrain.
3- Destroy the nearest airfield's ords prior to sortie.
4- Don't fire any of your guns unless absolutely necessary (and I mean even if its for a 100yards out enemy tank... its no good shooting down some tank just to end up getting spotted by a nearby Il2 or A20...)
5- Experiment bombing yourself and find out what the hardest vehicles to hit are doing.
6- Don't up a perked tank, of course.
The trick is not to get spotted... if you are spotted, no matter what you do, you will be destroyed one way or another. I'm a pretty good tank buster from the air and trust me, there ain't nothing vehicles can do without air cover.