Wet the floor for sure, keeps the dust down. Also, ground your car. You'd be surprised how much stuff will stay off if the car is well grounded to a good earth ground. If you can put a box fan or something in the window to pull the paint cloud out that will help, as well as keeping the garage door cracked about an inch or 2. Furnace filters make for a cheap and easy filtering set up so your paint stays inside and not all over the neighbor's car.