First of all, if you don't have the pc gamer demo of minecraft, get it. Load the world in the demo client, then once that's done exit out and go play the world in beta so you don't have limited time.
Hello! In this tutorial, I will show you how to find diamonds in the demo! NOTE: I have only found one so far. If you don't like being within 5 blocks of lava this isn't for you.
Step one: Acquire the tools from the chest.
Step two: Move five blocks to the left of the chest.
Step three: Dig straight down. Trust me on this one. It works.
Step four. You should come accross a diamond ore block just barely above bedrock. If you accidentaly fall in lava then go find some more tools and some ladders and try again.
Step five: Diamonds! :biggrin.gif: Enjoy. I haven't found any more than just that one but if you're someone who has never gotten a single one and is really desperate then this is for you. Bye! :biggrin.gif: