OK, so you have purchased a good pocket knife. You have spent your hard-earned money on it and presumably you would like it to last as long as possible and continue to give you great performance like the day you took it out of the box. Like any tool, a pocket knife is an investment. You probably thought long and hard at what type of knife you would need; what things it would be used for, and how much you could afford. As with any tool, especially one that you took so much care in choosing, you must protect it. You bought the knife, presumably, to cut things, so the blades edge should be your biggest concern.
Keeping a proper edge on your knife will require sharpening, and you have some choices on how to sharpen a pocket knife. First you have to decide if you want to sharpen your blade by yourself. Frankly some knives are expensive enough that a professional knife sharpener should probably be employed, but if you choose to do it yourself you will first need to collect your tools. When it comes to choosing tools remember that there are different ways to sharpen a blade depending on what youll be using your knife for, so when purchasing the following, dont hesitate to ask someone with experience if you are getting the right materials.
Before continuing take note that there are many electric, and manual, specialty (novelty would probably be a better word), sharpeners on the market. In some cases they may even work, but generally they are not recommended. Not only is their performance suspect, but there is something to be said for manually sharpening your knife. Using a whetstone and putting an edge on your knife can be a very Zen-like experience. Some knife-owners go as far as to say that hand sharpening your own knives shows respect and helps you form a bond with your blade. Regardless of your reasoning automatic sharpeners is generally a no-no.
First you must choose a sharpening stone. You may see them referred to as water-stones, whetstones, or diamond-stones, but they are all the same thing, a flat stone that you run your blade across to put a sharp edge on it. There are very wide selections of stones with a variety of prices. There are even sharpening stones with diamond edging that put a very keen edge on your blade, but are a bit more expensive. Each stone comes with a grit rating ranging from around 100 up to over 10,000. The lower the number, the coarser the grit, and the more material it will take off of your knife. The higher the grit, the sharper the edge you will get, but the more strokes it will take to do it. With a fine enough grit, your knife should be able to shave hairs off your arm, but that is not recommended. Coarse grits will take a lot off your blade, which may be ok for axe-blades or machetes, but finer blades usually require higher grits. Medium grit (around 800) is used to perform major sharpening jobs, while finer grits (at least 2,000) are used to fine-tune the edge to a razor-sharp finish. Once you become very adept, a stone with an ultra-fine grit (8,000 and above) will leave an almost mirror-like smooth finish on your knife blade. Sharpening stones can be found at hardware and sporting-goods stores. In general, try to find a large one at least 2.5 inches wide by 8 inches long, plus an inch in thickness. You should have some stone fixer on hand to repair your stones, and they should be stored dry, wrapped in a towel, and stored in a dry, oil-free place.
When using a whetstone it can be done dry in a pinch, but most knife sharpening experts recommend that you use a lubricant when sharpening your knife. The lubricant can come in a variety mixes, some water-based, some oil. Most sharpening literature recommends mineral oil as a lubricant. The reason a lubricant is used between the stone and blade is that it reduces heat from the friction that is created from drawing your blade repeatedly across the stone. This heat can warp your blade. Lubrication also helps clear out the stone and metal pieces, called swarf, that are created when the blade is reduced by the stone. You can find lubricants along with the stones and other general supplies like shining cloths.
Now that you have your stone and lubricant it is time to actually sharpen the blade. This is usually done in a couple steps. First you want to grind down the excess metal along the factory edge. To do this use a medium grit stone with lubricant and hold your blade at a constant angle while making your stroke across the stone. Work one edge at a time until you have created a fine edge with some catch to it. This means that you can feel some fine burrs along the edge. After you have done both sides with this technique it is time to actually put the edge on the blade. For this you want to use a fine grit stone also with lubricant. Maintain a constant angle this time also, but make the angle finer, or tipped up more. You will be taking less steel away from the blade so use even strokes and work from tip to tang. You test this edge by trying to slice a piece of paper, or carefully take some hairs off your arm. Once you have done these two steps you can put a mirror edge on your blade by stropping it if you want. You do this by running both edges rapidly across a leather strap. Once this is done your edge is complete.
Regardless of whether you choose to sharpen your blades yourself or having them done professionally, a well-sharpened edge is required for a well cared for knife. Once you start to sharpen yourself, buying a sharpening book is a great idea to become more proficient. Good luck and good sharpening.