We used to think we could DIY anything.  Really.  Anything.  Before our townhouse occupied most of our time, we repainted my car (it needed to be done, due to a blue hatchback/silver car/monster rust/no cash conundrum).  Before you wander over to the spray paint aisle, all inspired, know that we even used professional equipment.  Without the accompanying professional results, or timeline (it took us weeks).  Our "before" pics and progress shots were all taken with a disposable camera, but I can share a rough approximation of the before and awesome shot of the after:

Hot car, right?  If you like your '92 grocery-getters fierce and affordable.  This little guy's name is Charlie, he's a '92 Dodge Colt.

Here are our tips:
1.  Don't do it.
2.  But, if you must, don't use a spray gun outside in a field - rent a booth unless you want more bugs trapped in your paint than a piece of amber
3.  Go to an automotive paint store and buy all the proper gear.  If they say don't wrap up the parts you don't want to paint with garbage bags, just don't do it
4.  Spend the next four years sanding (rope in lots of family, friends, strangers -- there is enough work to go around)
5.  When you're finished sanding, sand some more (get allllll that rust and old paint off)
6.  Insert steps as instructed by professional
7.  Drive around in your fancy pants car

UPDATE - I was able to "digitize" (ish) my old pics, check out shots of the progress and Charlie in silver here.