Command & Conquer: Red Alert 2 Tips

Own personal zoo!
As one of the allies build a chronosphere. Then build qiute a large square out of walls. (You may also want to build a spy satellite). Get it so you can see the ore supply the enemy is using at the moment. When the ore miner starts sucking up ore, use the chronosphere to put it into the enclosure!

When used on computer they sometimes don't build another one and starve themselves of funds, but with a human opponent it just irritates them!

Do this with other units, but not tanks and stuff like that as they can break out. Unless your opponent can be bothered to come and rescue them, they are stuck there (as their machine guns cannot destroy the wall).

NB - Sometimes, if your enclosure is too small the unit will hit one of the walls on landing this means it will explode, but at least your opponent hasn't got it anymore!