LESS comes with a binary (lessc) that lets you precompile your .less files. You use it as such:
$ lessc styles.less > styles.css
But I think most people just use the
lessc -w or
lessc --watch command to recompile the CSS stylesheet automatically whenever the LESS file is updated. You can also have lessc minify the CSS, e.g.
lessc -w -x.
Edit: Just to clarify, lessc comes with the server-side install (i.e. when you install less via the node.js package manager). But you can download it manually from GitHub.
lessc is located at
/bin/lessc. This is of course a *nix binary (should also work for Mac), but there is a Windows binary (lessc.exe) based on dotless, which is another Windows LESS compiler.