Keep your medals low to remain under-level and avoid attacks from more powerful players. This will keep your resources safe and allow you to get more of them by attacking weaker players. Keep your biggest resource silos defended well. Position them near the center of the base, and force an enemy to break through at least two sets of walls to reach them. Ensure that the defending walls are as high a level as possible. Place mines as a decoy around the base to get the spies to attack them first, then take them out with your defenses.