The very first time you fire up the oven, it should be brought up to temperature gradually. Bring it up to 300F, and then after 30-minutes, increase the temperature by 50F, hold it at that temperature for an hour, then increase it by another 50F. Keep repeating this until you are up to full operating temperature. Once at full temperature, hold it there for a couple hours, then shut it down. The next time you use the oven, just set the temperature to where you want it, and wait for it to come to temperature. The gradual ramp-up in temperature goes a long ways in helping to prevent stone breakage/cracking and warping of the ovens superstructure.
Remember to toss some corn meal onto the deck to help season it if you are planning to bake directly on the deck surface.
Tom Lehmann/The Dough Doctor