Before Sharpening, Flatten the Back of Chisels and Plane Blades
It's impossible to get a sharp edge on a chisel or plane if the back of the blade isn't flat. If you're using glass and sandpaper, press the back side of the blade against the sandpaper and move the blade back and forth, being careful to hold it perfectly flat. Sand the back of each blade until it's uniformly shiny along the cutting edge. Do this with each grit as you move through the progression from coarse to fine. Use the same technique with natural or diamond sharpening stones.
Use a Handheld Sharpener On Kitchen Knives
Most of the time you don't need a power tool or an expensive knife-sharpening system to keep a workable edge on your kitchen knives. Regular use of a handheld sharpener is fine. This Wusthof sharpener costs $20 and works great. Other brands may work equally well, but we haven't tried them. This sharpener has carbide steel rods to shape the blade, and diamond rods to finish the edge. Follow the instructions to quickly sharpen kitchen knives that have standard beveled edges. You'll have to use another sharpening tool if your knives have unusual or asymmetrical angles.
Sharpen Serrated Knives With a Diamond Sharpening Steel
When using a diamond steel to sharpen a serrated knife, the curve of the steel has to fit the scallops on the knife. Take your knife to a cookware store and find a diamond-coated steel (about $30) that matches the scallop size on your knife. If you're shopping online, you can find the diameter you need by holding drill bits against the scallops. Then use this dimension to order the right diameter sharpener. Another option is to buy a tapered, pocket-size diamond steel that accommodates a variety of different scallop sizes.
Notice that one side of the blade is flat and the other tapered. Sharpen only the tapered side. Starting at one end, sharpen each scallop with two or three strokes, matching the original angle. When you're done, run the knife through corrugated cardboard to remove metal filings.