The mooWalkthrough is broken down into sections. Each sections builds off the last section, and each page builds off the last page before it. You should read this like a book for the most part, each page, going in order. As you've probably noticed, there is a Next Page link at the bottom of every page.
The section list below is not followed strictly.
How to Make Cool Pages
How to Make Cool Scripts
How to Make Classes and More
The first section is a walkthrough of DOM, Effects and Ajax, and a few other things. We've found that these are common things people like to use on their pages, so these should be covered first. Once you have learned about how Mootools interacts with the DOM, how to use Effects you should be well able to add Mootools to any website or web page. (Maybe even the iPhone or some other exotic use?)
The second section is aimed towards those who are still reading, those who want to use more then just some cool Ajax and pretty effects. The second section goes deeper into Mootools, going over many functions that even it's self uses to simplifiy it's code. This section is really great too know.
The third section is aimed for those who really want to take Advantage of Mootools. It explains Mootools Object Orientation, Classes, Extending, and Implementing.
As disscused on the last page, you should have downloaded Mootools. This [at time of writing] walkthrough uses 1.2.
If you find any errors, please feel free to email me at daybreakmaster [at] gmail [dot] com. Or you can find me in the IRC Mootools Channel! Server: irc.freenode.net, channel #mootools.
You can also register, and then edit what you believe is wrong. :)