Dull knives are annoying and actually more dangerous than sharp ones. You end up pushing harder, which means you're more likely to slip. This video from Tasty covers three ways to keep your knives in good shape, from a quick hone before each use to a full sharpen on a whetstone when things get bad.
A honing steel doesn't sharpen your knife. It straightens the edge, which bends a little with regular use. Put the tip of the steel on a towel on the counter for stability. Hold the knife at about 20 degrees - start at 90, cut to 45, cut again to roughly 22. Drag from heel to tip on one side, then the other. A few passes is all you need.
Tip
Hone your knife before every use. It keeps the edge aligned and means you won't have to sharpen as often.
For a quick sharpen, a pull-through sharpener is the easiest option. It has a coarse side and a fine side. Put the knife in the slot, pull it toward you with even pressure, heel to tip. Do the coarse side a few times, then the fine side. Keep the knife straight up and down - don't wobble.
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Good for regular maintenance, but if the blade is really damaged you'll want a whetstone.
If your knife needs real work, a whetstone is the way to go. Soak it in water until the bubbles stop coming out. Set it on a towel so it doesn't slide around. It has a coarse side and a fine side, same as the pull-through. Start coarse.
Hold the knife at 20 degrees against the stone. A paper trick helps you find the angle - fold a corner of paper in half twice and that's roughly 22 degrees. Drag the blade from heel to tip in a sweeping motion, then flip and do the other side. Keep even pressure and add water if the stone starts drying out. A few passes per side for maintenance, more if the knife is really dull.
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If the stone starts making a scratchy sound, splash more water on it.
Grab a tomato and try slicing it with different parts of the blade. If any section catches or feels dull, go back to the stone and focus on that spot. A sharp knife should glide right through without squishing the tomato at all.
Don't toss your knives in a drawer loose. They'll bang into each other and dull fast. Use a knife block, a magnetic strip, or blade sleeves if drawer storage is all you have. When you put a knife in a block, slide the spine in first so the blade doesn't drag on the wood. Hand wash your knives and dry them right away. Skip the dishwasher.