I give a repo a star if it's something I use or think there's a pretty good chance I'll use in the future (bookmarking). It also means I like to stay up-to-date

I give a repo a star if it's something I use or think there's a pretty good chance I'll use in the future (bookmarking). It also means I like to stay up-to-date with their development, as least at the surface level. I built http://sibbell.com http://sibbell.com for exactly that purpose - it will notify you any time a repo that you star (or watch) has a new release. I don't like to "watch" repos on GitHub though because on a project of any size, you get flooded with emails...