Basical this tut shows you how to download and install a minecraft mod menu. http://www.youtube.com/watch?v=2kN-UHxj5pc
These mod menu is like a call of duty one, but better. This mod menu includes, god mod, fly, xray, aimbot and many more.
When you join the game it will say [c]player has joined the game. That will be the name that shows when you talk or press tab. People carnt see [c]player they can only see your real name. so dont worry about that.
to use this mod menu press tab. or backspace..

http://www.youtube.com/watch?v=2kN-UHxj5pc
http://www.youtube.com/watch?v=2kN-UHxj5pc
http://www.youtube.com/watch?v=2kN-UHxj5pc

Watch this for a tut on how to downloads and install it...