Personally, I keep just three knives in my kitchen, which serve for all my personal and professional purposes: A small paring knife, which is used for zesting, peeling and cutting small foods; A serrated knife, which is used for slicing breads, tomatoes and shoes (not really); And a Japanese chef’s knife (although French is also quite popular) for virtually all other purposes in the kitchen. Of these three knives, only one ever needs to be sharpened: The chef’s knife.
There are two parts to maintaining a sharp (and thus safe) knife: Sharpening and honing. Sharpening a knife actually changes the shape of the knife’s edge to make it sharper, whereas honing simply realigns the metal ions of the knife and refines the edge.
You can spend a month’s worth of rent on various sharpening tools for knives, but I contend that simplest is always best. The whetstone, in this case. The whetstone should be soaked for a half-hour in water, and then shaken dry. There are two sides to most whetstones, the coarse side and the finer side. Start on the coarser side if your knife is very dull, and then sharpen on the finer side next.
Now, on to the scary part: Sharpening the knife
Hold the knife at a 10 to 15 degree angle, with the blade facing away from your body and push the full length of the blade away from your body, along the stone at a diagonal. At the end of that stroke, gently turn the knife over and repeat, always stroking away from your body at a diagonal across the stone. Start with the coarse side of the whetstone, and then do a few rounds on the finer side. If needed, wipe your knife with a cloth to remove any debris.
On to the fun part: Honing
When your knife’s edge simply needs a picker-upper (every two weeks or so), or after you’ve given it a good sharpening, you’ll want to hone it. The honer is found in most knife kits, and it’s what you see chefs using when “sharpening knives” on TV or in Benihana. It's the long, stainless steel rod that’s rounded with a rubber handle.
Hold the honer in one hand and the knife in your dominant hand. Holding the honer horizontally away from your body, draw the blade of the knife downward along the honer, using light pressure as you stroke the length of the blade downward along the honer’s surface. Maintain the same 10 to 15 degree angle for your knife, which will feel like the knife is almost completely flat against the honer (but not completely).
Repeat this motion with the other side of the knife blade, always stroking the knife downward and pulling away from your body. Use a towel to remove any residue on the knife.
To check that your knife is well sharpened and honed, test a slice of a tomato. If it easily slides into the tomato’s skin, it’s ready.
Remember: A sharp knife is a safe knife. When all else fails, just take it to the local knife shop for a proper sharpening. We won't tell anyone.