Defend your base with upgraded units. Surround your base with barriers in order to make it difficult to penetrate. Placement of defensive structures is important, as well as upgrading defensive towers. Strengthen your base starting with the most important structures. Focus on the Command Center (if you care about Ranking points) and resource buildings. Place silos and resource producing buildings behind walls, together with all the defensive buildings available. Leave the Command Center outside to enter quickly in protection mode after a player takes it out for points (and thus protecting your resources). Leave space between defensive walls and your structures. Attacking troops will usually take time to take out the wall and not shoot over it. Place all non-essential buildings (Research Lab, Barracks, etc) outside your main area to serve as decoys. Leave spaces between them to spread out the base layout as much as possible to force enemies to take more time to take out all your structures.