"Breaking in" your new pipe simply means developing a thin layer of carbon or "cake" on the inside wall and in the heel (bottom) of the bowl. The carbon cake acts like a grate in a fireplace to improve the draft and ensure complete combustion. It also serves as a barrier between the burning tobacco and the bare wood. Many pipes are pre-carbonized to assist you in the bread-in process.
There are several methods of breaking in a new pipe. We recommend beginning with a full bowl of tobacco. The most important thing is to smoke the tobacco all the way to the bottom! SMOKE SLOWLY. Tamp and re-light as often as necessary; do not be afraid of using too many matches. If your pipe gets too hot, let it rest awhile; then tamp the dead ashes and re-light. You can test if the pipe is too hot by placing it against your cheek. If it is uncomfortably hot, set it aside and allow the pipe to cool.