How to stop Minecraft lag!

Hey there, fellow PlanetMinecrafters. My name is Alex, and despite my fairly high pitched voice, I'm fairly mature. I made a tutorial today on how to stop lag for Minecraft, it's very simple, a 4 minute tutorial, and I'd love you to check it out to tell me what you think of it. Thanks alot, it really helps:)

http://www.youtube.com/watch?v=2a4r68z-NzY