Spreading out munitions:
Do not give too much of the powerful items such as tank mines, C4, anti-tank guns, etc. to a single person. If you have this person advance and he gets taken down by a tank, your other teammates might not have the firepower needed to even get close to the downed person, let alone heal him. It is always a good idea to have each teammate equipped with at the least one high powered explosive in case you need to take something out.

Change soldier color:
You can change the color of your soldier from white to black or black to white by blowing him up with a grenade and finishing the level. Note: He will lose experience -- do this early.

Destroying heavy armor tanks:
Find the man with C4s and give his detonator to someone else. Keep everyone back except for the man who has the C4. Quickly run to the tank and plant the C4. When you are finished, get another troop to call him back. When he runs back, the tank should be focused on him. Change to the man with the detonator and use it. If this works, everyone should make it out alive. However, if he does not make it, you can clear the area then heal him.

Charge the enemy:
The game sends an infinite amount of troops after the alarm has been set. The best way to defend yourself is to charge ahead as fast, but also as safely, as possible. In some levels you can cut down the number of men by almost fifty. If you are low on ammunition, health, etc., this is a good way to cut down on the amount of men you have to deal with. It also works sometimes if you send a man far ahead and hold him there, then do your objectives for your mission.