

One or two layers above the bedrock, so you don't have it interfering with your work, you dig a long tunnel, 2 high and 1 wide, which will serve as the trunk.You dig down to the bedrock, because that's where you're going to find the most different kinds of stuff.Here's a brief description of branch mining: There's a mathematical analysis on it in the official forums (the link is to an archive of the post).
