I am now going to tell you how to make a simple capture trap on minecraft. First make a long passage that is 2 blocks high and 1 block wide. It should be filled in at the end and should be in a cave so your target player should mistake it for a mine/dungeon. It should be at least 5 blocks long. In the middle place a pressure plate and redstone on both sides. The blocks on either sides should be obsidian or bedrock. Under the obsidian/bedrock should be a piston (sticky if you want to use it again). Then put a sign on the end of passage that the player enters through that says "Diamond Mine", "Gold Mine", "Obsidian Mine", or "Danger: Do Not Enter". People can't resist whats bad for them, after all. The person in question should go in, step on the pressure plate, and get trapped when the entrance/exit becomes 1 by 1 and too small for the poor sucker to get out of. Check it every now and then and if there is a player/mob stuck in there, if there is, shoot with a bow or put lava in it. If you want to use it again, remove the lava, and put a lever next to the pushed up block and pull it. This only works with sticky pistons, so be warned. Now, claim your loot and walk away. If you want to prevent tunneling, place lava behind the wall.