A new BBQ pit should be cured like a new iron skillet. You may chose to rub the inside of the pit with Pam, peanut oil, cooking oils, or even bacon grease left over from bacon cooked on the stove. Then you light the pit with a medium fire, say 220 degrees for those of you with smokers. Choke the smokestack control about 1/2 and let it smoke heavily. A few hours is good, the longer the better. A Pit will cure without oils, but the buildup of the resin base on the doors doesn’t seem to hold very well over the years.
I have made maybe 100,000 BBQ pits, noticing the pits seated with oils seem to produce better results. Once again, be careful with green woods. Some will produce very bitter tastes. Please do not ever use green mesquite in a smoker.