I start by wiping the entire interior of the fire box, cook chamber, door(s), and all internal accessories (racks) with a damp cloth (no soap), to remove dirt, dust and any packaging remains. If it's very dirty, starting with a shop vac first is a good way to go. Then, wipe or spray the cook chamber with cooking oil (any cheap stuff will do).
Start the fire low with some chip or chunk smoke wood. Keep the temps as low as it can run, and keep exhaust vent(s) partially to fully open.
The smoke wood will do 2 things: Give you an idea how your rig will like to run and form a light film on the cooking oil which will build up for better smoking later. The oil helps to seal the paint so it shouldn't give off vapors into the food later on.
Gradually increase the chamber temperature after the first hour or so, to achieve a temp at least as hot as you will smoke at. Take a few hours to raise the temp for good results. I go about 50* above this. If you will be smoking birds @ 300-0325*, then take it over this temp to assure that the paint will be cured and not release harmful vapors later during normal smoking.
The longer you season it the better.
Oh, don't forget to prep some goodies to toss on the grates while she seasons up. Then you can try it out for the first time on something small for a quick smokin' treat...and you won't be wasting the fuel you burned to heat it up by just letting it go, all cold and lonely.
Congrats on the new rig!