Alot of board members will tell you that you that when you cut a shroom up each piece should include part of the mouth. Personally, I disagree, and have had great success just slicing and dicing randomly. I know it sounds crazy, but it's the truth. On occasion I will pull a piece of rubble w/ shroom attached and chop the shroom into 4 random pieces. I'll drop the cut pieces in the tank and sooner or later (within a week or two) the pieces will attach and start growing. One important note is that if you use this method, I strongly advise using prefilter sponges on all filter/powerhead intakes, or you'll never see the cut pieces again.
The easiest way to frag shrooms, though is to cut straight down the middle of the mouth, but leave the shroom attached to the rock. Cut all the way down to the base of the stalk. It's hit or miss, but usually you will end up with two seperate shrooms. Occassionally the shroom will grow together again. This method does not allow you to place shrooms randomly throughout the tank like other methods will, though.
HTH
BTW, there is a recent thread about fragging shrooms. It covers another popular method using netting. While that method is popular, I prefer to let my shroom pieces float throughout the tank and choose where they end up. Sometimes it's not the most desirable location, but it's the easiest way for me to do things.
