Because good knives are a big investment, it's crucial that you treat them with care. Not only does sharpening knives keep them performing up to their full potential, but it also makes them easier to use. Sharpening involves two separate but complementary processes: using a steel -- a metal rod with a finely ridged surface -- and a whetstone. The steel doesn't actually sharpen the knife: It hones the edge, realigning it and removing nicks and dents. It's best to steel every ten uses or so. Use a whetstone to sharpen the blade every two to three months, or when your knife barely makes a dent in a tomato's skin.
To steel, draw the knife along the rod, making sure to keep your fingers behind the shield. Look carefully at the blade before you steel. It's important to know its profile, so that you can respect the angle of your blade and the gentle curve at its tip. Give it several good strokes.
Using a whetstone will take more time. Lubricate the stone with a few drops of water or mineral oil; after you've started using one lubricant, don't use the other until you change whetstones. Start with the coarse side of the stone up; lay the heel of the blade on the bottom right-hand edge of the stone. Sharpen the entire edge by holding the knife at a 20 degree angle with one hand while guiding the blade with the other hand. Turn the knife over; repeat, starting with the heel of the blade on the lower left-hand edge of the stone. After 10 to 20 swipes on each side, repeat these steps on the smooth side of the stone. Finally, give the blade a few passes over the steel to remove any loose bits of metal.