from How to Cook Italian, by Giuliano Hazan
1. Hold the knife close to the blade with your index finger on the blade itself for better control
2. Hold the food with your fingers curled in so that your knuckles are touching the blade, not your fingertips.
3. Always move the knife in a back and forth sawing motion rather than just pressing down with the blade. You use considerably less pressure, making cutting safer, easier, and more precise.
4. Whenever possible, keep the tip of the knife on the cutting board using the knife in a rocking motion. Anchoring your knife keeps it steadier and gives you more control.