Job one is to play through the tutorials. This is a tough game/simulation
to master. You'll never do it if you haven't worked through the tutorials
first.
Keep your tanks away from trees and buildings. Those hide infantry, and
infantry can be bad news. On the other hand, if the woods have previously
been cleared, placing tanks on the tree line can provide good cover. Don't
underestimate the power of artillery.
Even simple HE rounds can cause your opponent to button up, which greatly
reduces his or her effectiveness.