Minecraft wiki entry for Multiplayer_PvP_bases, associated text: You need to find the enemy's base. This may be the hardest part. Send out trackers and spies to find any enemy activity. Then hunt relentlessly and look into any odd landscaping or other signs. Signs can be things like flatter-than-usual mountainsides indicating Jeb doors, 1x1 lava pits that may cover a pressure plate, and weird landscaping (hills in a flat biome). One good tip is to always be suspicious. Or, if you get raided, just stalk the retreating attackers home.