Command & Conquer: Red Alert 2 Tips

cheap and better flak cannon alternative
If you play as one of the soviet nations, never build a flak cannon (defence tower), it will take up more power and it is expensive.

A cheaper 'flak cannon' is to build 3 flak troopers and surround them with walls or just make them patrol a small area. They will fire three shots together compared to a single shot from the flak cannon (I am not sure if one flak trooper inflicts the same damage as a flak cannon does, but I recommend something cheap and effective).