How can I analyze JavaScript code of Facebook and create some hacks for Greasemonkey?

What tool should I use? And how should I use those tools? I'm very new to JavaScript and I would really appreciate some detailed instructions. It will be greatly appreciated if there is a tutorial anywhere.

Try installing the Firebug add-on for Firefox and get familiar with it, that's a great first step.

The Firebug site should have some more detailed information.

http://getfirebug.com/