A good knife should only need to be sharpened once or twice a year. The rest of the time, you can simply restore the knife's sharp edge with a steel. (The difference is that sharpening actually scrapes metal off the knife while honing it with a steel just straightens the blade.) Sharpening stones are readily available at most kitchen supply stores.
Before sharpening your knife, test its edge. This way you'll have a point of comparison when you're done sharpening. You can do this by slicing the skin of an apple or tomato to see how much resistance you get.
Next, run your sharpening stone under water and set it on a dampened dishcloth. Running it under water reduces friction, which can heat up your blade and cause damage. The towel holds the stone still while you sharpen.
Start by holding the knife in your right hand with the blade facing away from you. Set the heel of the knife against the upper left corner of the stone. Tilt the blade until it's at a roughly 20-degree angle to the stone.
Maintaining this angle, pull the blade toward you and across the stone, ending with the tip of the knife in the lower right corner of the stone. You can rest the fingers of your other hand against the flat of the blade to help guide it.
Some things to keep in mind:
• Keep an eye on that 20-degree angle. Too perpendicular to the stone and you'll just dull the edge further. Too little and you won't make enough contact with the stone to sharpen it.
• Be sure that the edge of your knife is making contact with the stone at every point along its length.
• When testing the sharpness, test at the tip of the blade, the middle, and the back to make sure it's evenly sharpened.
• You may need to adjust the exact position of the blade on the stone depending on the size of your knife and its handle. In these cases, just follow the same motions as described above.
(Images: Emma Christensen for the Kitchn)