What's the easiest way to learn Ajax?

The equivalent question several years ago was, "What was the easiest way to learn and write HTML?"

How do you display tables in a web page? Go to a page with tables, view-source and write the same. Alternatively, if its too tiring to surf the web for the feature you want to copy, just fire-up FrontPage or DreamWeaver (blasphemy!), create what you want (e.g. an image map) and view source. Tada!

Now, what's the easiest way to learn Ajax? e.g. the google suggest-ish auto-complete.

Simple as 1 2 3,

1. Do it in Rails once: 3 steps demo (.mov file) or O'Reilly tutorial
   
2. Copy the HTML (view-source), the javascript files (yes, the ajax javascripts are MIT licensed, aka you can do anything you want) and
   
3. Re-implement the server-side yourself (this is the familiar part for most).

And of cos, arm yourself with some Ajax Debugging facility just in case.

Examples are plenty: Drag-drop shopping cart, Drag-drop list, Upload progressbar, and many more