How to build your first project using ExtJS framework? Here’s shortly all instructions to quickly start a project using ExtJS libraries.

First of all, download SDK libraries from the ExtJS site. In the archive you’ll find install instructions; simply you’ll need only these files:

• ext-base.js, from adapter/ext folder (or another base if you’ll use it combined with another framework)
• ext-all.js (compressed version) or ext-all-debug.js (obviously for debugging)
• ext-lang-xx.js from folder source/locale to get ext in your language
• resource folder (keeping only default themes and only ext-all.css file)

Now to use it you can just create a web page and include the 3 specified .js files, in the same order as written above. Then include ext-all.css in the page, and voila, Ext is installed in your page.

To begin, read some tutorial, and start with the examples you find online, or also in the same SDK archive file. The API documentation is available online, and also offline (you need to install AIR support). A good resource to get confronted is the community forum, and a custom google search on it.
For the development you’ll need a JS IDE, I suggest Spket, standalone or included as plugin of Aptana or Eclipse. In Jack Slocum’s blog (ExtJS founder) you’ll find all instructions to install the IDE and to configure a Javascript Profile to get autocomplete for ExtJS. There’s also this page where you can find a lot of resources.