1. Do cool things.

2. Tell people about them.

There's a pretty big industry surrounding how to promote yourself effectively, but ultimately, most of those things are secondary concerns. You shouldn't ignore marketing advice - there's often useful insights on what appears impressive to other people - but you'll always get more bang for the buck by actually doing things that are impressive to people rather than trying to make what you're doing appear impressive to others. Actions speak louder than words.