I would like to use LESS, the CSS preprocessor, with Drupal 7 projects.
What are the required steps to use LESS in Drupal?
There is the LESS CSS Preprocessor module for drupal.
Note that the mentioned module doesn't use the normal Ruby compiler but a PHP compiler with some differences.
You could also make use of the LESS .js compiler while developing. Just include the .js file supplied by LESS, as explained on their website.
Be careful using any LESS modules for Drupal. One error in your less file could bring your whole site down. And it can make debugging a pain in the rear.
Many people, myself included, recommend isolating LESS from Drupal by using a LESS compiler to watch your less files, and compile to pure CSS files that you can deploy to your staging and production servers.
less.js running on node.js works great for my workflow in Ubuntu. The answer above details how to do this.
For Mac, try: http://incident57.com/less/
For Windows, try: http://winless.org/
Introducing LESS support in Drupal 7 would be a great idea when combine with Bootstrap and Font Awesome. A helper module named "TWBS LESS". The goal of TWBS LESS is to provide a handy support for LESS and act as the helper module for on going Drupal-Bootstrap-Remix development. http://edin.no-ip.com/blog/hswong3i/announcing-twbs-less-simple-less-support-drupal-7