Well, my wife and I are getting ready to move, and I have this beautiful canvas of a completely unfinished 2 car garage to work on.
First thing: get yourself some cabinets to hang up on the walls. Make sure they're high enough that they dont interfere with the car doors opening and closing. Also, make sure you get cabinets that are consistent with what YOU need to store. Plan things out in advance. I'm doing cabinets on one side and shelving on the other, most likely.
As for shelving: get something that will be sturdy - dont buy that pressboard stuff, because the second you spill brake fluid or fuel or oil on them, they're toast. Get a good quality metal shelf. Also, rubbermaid makes a hanging system that I'm looking into. its adjustable for different kinds of hangers, and if you screw it to the studs, it's VERY sturdy. Great for rakes, power trimmers, spreaders, etc.
I'm also building an area for bike stuff. Essentially it's going to be an area for jackets, gloves, boots, pants, and helmets. That wa all my gear can stay in one centralized place without having to put any of it on the floor.
As for the floor itself, I'm having the floor professionally sealed with an epoxy. It's kinda like what you can buy in the can at lowes (made by rustoleum) but the professional grade stuf works MUCH better, from my experience. It'll hold up to a kickstand being put on it without chipping and/or scratching.
With anything like this, you have to consider your budget as well. it would be EASY for me to spend 20 grand or more in my garage, but im not going that high dollar. If you want it, they even have diamond plate aliminum cabinets, but you'll pay dearly for them...