If you didn't draw very useful spells at the beginning of the game, start collecting the Open Plane Wall and the Chobolo spell.

I usually send two warrior out together to one side of the board and an archer out to the other side of the board. I have seen many people successfully keep all their warriors together and attack enforce. The only problem is that it usually leaves the wizard open to attack from the other side.

Many people find that collecting all the cards in their spell deck is useful. These are usually defensive players.

The following spells are great for finishing the game:

Confusing Identity. Send a powerful warrior up to the end tower and cast confusing identity once that warrior wins.

Teleport. If you are playing the water wizard. Load up on your free waters and teleport to an empty castle to end the game. Chances are that people will figure out what you're doing quickly and fall back to their main tower for a strong defense. Try combining strategy.