Well, mine's 20x24 and it still feels really small. I keep my race car there when I'm not working on something. I have fold-down benches (one for wood, one for metal) on the side where I keep the car so that I can turn it into working space when it's needed. I did storage above the garage door and also on the walls. On the driver's side door wall, I moved the storage up high enough so that I wouldn't hit my head on it when I was walking around the car.
I divided off the other half of the garage with some stuff (table saw, tool storage, shelves) that would normally eat up wall space. On the work-only side, I put both a bench and a work surface that doubles as a drafting table.
My advice is to keep the storage up high, except for things you need access to on a regular basis. But benches under the storage if you've got room.
I also built a shed for the sort of lawn-and-children stuff that ends up as something to trip over if you let it inside the garage.
You can see pictures of mine on the link in my signature.