To get started, I just downloaded a copy of CodeKit (OSX) and dropped a couple theme directories into it. When that happened, CodeKit started to watch all the LESS and SASS files in those directories- and automatically compiled them into actual CSS files whenever I saved.
To become more familiar with the syntax, I forked a copy of Jared Erickson’s LESS theme on GitHub and made some edits. Then I converted it to SASS syntax. If you’re completely new both SASS and LESS- I think that’s a fun small project to do.
I didn’t get deep into the mixins and nesting, but I already see several ways it could improve my workflow. And honestly, I was just as impressed with the CodeKit UI and features- like live browser reloading, file minification, etc.
Just so you have no reason not to try it too, I made a short video showing how to take a regular WordPress theme and set it up to start using SASS files with CodeKit: