To my knowledge, the most common alternative to manual installation (see the section below) is CKAN (The Comprehensive Kerbal Archive Network). Subscribe to the blog and follow me on Twitter to get news of any incompatibilities I encounter when using KSP mods (and hopefully solutions!).
These are the basics along with some of my own recommendations on the process. There are already many great modding guides available scattered about the Internet, so I’m not going to try to make an attempt at a comprehensive guide.
