OK, So I know how to Geomerge, but whenever I do it, it is all messed up and uneven. How can I make it straight?
When you are at the stage where you are actually pushing the box into the ground, press a on the box, and immediately save and quit the game. If done correctly, the box will be perfectly geomerged. If you don't know what I'm talking about, here's a video by a premium, Bl00D F1R3, that shows you how to do this. http://www.youtube.com/watch?v=RSAEpNYImbQ&feature=related
Just an add on to what Psyco said: The save and quit thing is a glitch. So when you follow the video and the instructions, know that you can fully count on it in ANY geomerge. It works perfectly every time. That is how people make professional maps that get popular on the forums.