The best chocolate is sold in bars, and must be chopped by hand for even melting or to be added into a recipe. The best way to chop chocolate by hand is with a large serrated (aka bread) knife. Working on the corner of the block, chop down with some force as if your knife were a paper cutter. For the most control, hold the knife handle with one hand and rest the heel of your other hand on top of the blade at the tip of the knife for leverage. Chop away the corner, then move the next corner, and so on. In most recipes, the goal is to get the chocolate into approximate chip-sized pieces.
Occasionally a finer chop is required. Once the chocolate is in chip-sized shards, run over it several more times with the knife in the same manner until the desired granulation is achieved. Chip-sized chocolate can also be put in a food processor. Pulse it on and off until you get the size you need. Too much processing will melt the chocolate with friction.
Never dig the tip of your knife straight into the chocolate – it can be just as damaging to the knife as any other hard surface.
If you do not have a serrated knife, use a chef knife. Do NOT get sucked into buying a chocolate fork for chopping. This is a stupid tool designed to take your money. It is actually an ice carving tool, which was re-purposed “to make chopping chocolate easier.” HA! It only works if you have a mallet or hammer too, and it takes longer! Money grubbing bastards!