I have painted several cars.  In my opinion, trying to rig up a temporary paint booth is a waste of time.  It is not going to help that much.  Anything short of a fully enclosed professional booth with explosion-proof fixtures MIGHT get 10% better filtration than nothing at all.  Just choose a very still day, do it early in the day, and make sure your neighbor doesn't start his lawnmower while you are painting.  Most paint jobs get sanded and buffed anyway.

I agree with MS, most are not worth the effort. Nothing beats a little housekeeping though. I usually take the garden hose to the whole place on the day before, walls, ceiling, lights, everything! Sweep out the water and let dry overnight. I do staple one of those cheapy plastic really thin drop cloths to my ceiling over the area where I paint. My shop is two story and the upstairs has become quite a storage area and difficult to clean. The plastic stops any drop throughs. It also tends to catch a lot of dust with the static that it attracts. I made a little frame to put filters in the man dooropening and have a big exhaust fan in a back window. I make sure the neighbors are not grilling when I paint. And yes a still day without too much humidity is a great thing. I tack myself off first and then the car (really helps). I think the day you pick has a lot to do with it so the wind is calm and not rocking your building and shaking all the dust loose. Also, not a good idea to paint when the pollen is high, there is a lot of that crap in the air certain days. Another thing that helps is to ground the car really good. I sacrificed a nice extension cord and put a ring terminal on the ground so I can hook the car really good to the service ground in my building. It really helps keep the static down. It suck when you make a pass with your expensive paint and then watch all the dust in the air race to your just painted surface because of the static.