I open everything at first. Get the coals and split on and let 'er start heating up. Then I close the door closest to the firebox and I close the firebox door almost all the way, just leaving it cracked. As it heats up and starts drawing, then I close the other door up top and the firebox door, leaving the damper on the stack full open. I let it roll like that until it's up to temp and I have sweet blue smoke. It's usually 45 min to an hour. Last time, I tossed two splits on initially, since they were small, but they were very dry and I had the pit at 325 for awhile before it started trending down. So I let it get closer to 275 before I tossed the food on, and that was almost 1.5 hours since I started the coals.
The intake on my firebox door is a channel with two bolts controlling how "open" it is. On mine, it's pretty far open, you can stick your pinky finger in up to the fingernail, but I"m at 6000 feet, and that's where it seems "happiest" (based on how light the smoke is.). I don't use the damper much. I set a temp and use it a little to fine tune the temp. It's usually 3/4 open. If I close it too much, I start getting nasty smoke, so I try to control the temp with the wood I put on.
Remember, I'm new. This is my first summer with it. One thing I learned is to get a good, clean fire and find out what temp the pit likes. It's been FAR easier to cook at 250-260 than to try to push it to a different temperature. If I have to do something in the kitchen or just get distracted, it's much more forgiving and I'm less likely to come back to a strange temp.
UDS / Jambo Backyard / Red Thermopen