I was compelled to write this section as the outstanding majority of games are decided in tank vs. tank battles. Just driving your tanks in the direction of your opponents tanks and then hoping you will overcome your opponent is not a good attitude to take. Anyone can build a large group of tanks quickly; but it takes a skillful player to know how to use them effectively. Knowing how to use your tanks properly is essential. They are the most important attacking unit in the game.
Drive by shooting: In Red Alert 2 the "Drive By Shooting" is when you drive your tanks past your enemies tanks rather than head on into them. This means that your tanks will automatically target the enemy tanks as they drive past, whilst the enemy tanks will all (unless the player is quick) end up chasing the tank at the front of the line (allowing you to seriously damage the enemy). Send dogs towards the enemy tanks before you do this, it will waste a lot of their fire and make life a lot easier for you. The tactic isn't a good idea if they have a lot of dogs etc mixed up with their tanks. Also think about the possibility of driving around structures etc to prevent the enemy from hitting you (particularly useful if you've got a group of drones on your tail). Don't use the tactic in very confined spaces or else it could backfire. This tactic works from 2 tanks upwards.Anti-Drone Tips: Apart from building and using other units (not what this section is about), the best way to combat drones with tanks is to run away from them! Drones auto attack any enemy unit that comes in range. Hence if you send a decoy such as a dog and then run it across the path of your tanks then your tanks will shoot it to pieces. However, if an enemy sends a group of drones at you, the best thing to do is to immediately drive in the opposite direction; as tanks have turrets they are still able to shoot at the drones even if they are behind them. If tanks are moving in the opposite direction to a drone then the drone will struggle to jump into the tank - and whilst it is struggling behind the tank it should be shot to pieces. Another obvious tip if a drone does get in one of your tanks is to force fire on that tank to kill the drone inside it, otherwise it will keep hopping from tank to tank. Drones are a lot cheaper than tanks, yet they have the ability to shred them apart. Drones are slower on ore - hence if you drive your tanks over an ore field with the drones chasing you, they will be shot to pieces. You must keep an eye out for drones and use your tanks as I have just mentioned.
Distraction Tips: A vital part of any tank battle, is the use of 'decoy units'. If you fail to use decoy units then your opponent will have little problem in wiping out your force, especially if he is using decoy units. Decoy units should be any that you have and don't need - such as spare infantry units. The best infantry units to use in tank battles are dogs - they will attract a lot of the enemy tank fire hence allowing you to get in more shots than your opponent. Dogs can turn the tide of any tank battle, be it one tank versus one tank, or thirty tanks against each other. Another possibility to consider (if you have surplus miners), is to throw your miners into an attack. They will, like dogs, attract enemy fire, and will be able to take a large amount of damage.
Grouping: If you are going to be in a large tank battle (lets say ten tanks or more), then an effective tip is to split your tank groups. I suggest splitting them into groups of five (grouping wise - not physically). Once the tank battle starts you can order one group to attack a tank and another to attack another. This will save you from wasting shots by selecting all of your units. It will also stop your units just randomly firing at tanks, as it is much better for concentrated fire upon one tank (resulting in destruction of this tank) than to take a few shots at every tank in a battle.
Attacking First: Lets say your opponent's tanks are all huddled together in a group a small distance across the map from you. He doesn't appear to want to attack. Well attacking first is better, for if you instigate a tank battle then you automatically take out the first few tanks that you ordered your units to take out. So you already have an advantage. Your tanks will now keep on firing at the tanks at the front of his group whilst his tanks behind his first row or two will have to be ordered to come forwards.
Manoeuvres: Many players do not appreciate the fact that tanks can be split up and sent to attack in different directions. Lets say your opponent has one large group of tanks, you could split your tanks into a group of two and then attack his large group at both sides. This means that his tanks in the middle are doing nothing - until he tells them to; hence you have a few extra seconds in which to get those few vital kills. Other manoeuvres that are useful include the blocking up of small gaps. Lets say, for example, that your opponent is about to send his force over a bridge or through a small canyon. Place your tanks at the entrance to the bridge or canyon; his tanks will not be able to attack all at once as the bridge/canyon is too small. Hence your tanks will be able to destroy his with ease, much better than allowing your opponent to drive through and use all his force at once.
Out numbered: In a situation where you are out numbered (by a large margin) and there is absolutely no hope of victory, the only viable way to win a game is to attempt to destroy all of your opponents base (unless the game was set up via a lobby and has last unit selected). To do this you have to bypass his tanks. So try driving them somewhere where his tanks cannot reach yours, then go for his base. If he only has one base then this tactic may well work. However, if he has several bases scattered around the map then it will most likely not work. The opponent has to make the decision of whether he should destroy your base or attempt to get your tanks. This tactic should only be used as a last resort!
Summary: Anybody can click on tanks and build them. Good players know how to use them to their best advantage. Tanks are what decide almost every game of Red Alert 2. If you don't know how to use them properly then practice - if you can't handle tanks, you will never be a great player.