After the comment of David Sword I realized that doesn’t exist a best way to use LESS on a WordPress theme, but several ways to do that. And a good way is to use the resources of a good text editor. I’m used to work with Sublime Text 3 but after trying several times to make it work with no success I decided to use another text editor, Crunch 2, and with it I didn’t have any problem to compile the .less file to .css, as this is a normal feature of the free version.
