How do I maximize my garage space?

I have come to the realization that I gradually turned my garage into a storage unit. It didn't happen overnight, of course, but because I am the kind of person that tends to hold on to stuff. Honestly, I'm not yet ready to throw out most of my stuff yet.

It's a two-car garage, and I'd like to create adequate space for at least one car and a mini workstation. What Things Can I Store in my Garage? What Shouldn't I? I'd love to read how other people go about it and how to create order from the chaos.