Sharpening Your Wire Cutters
Many people recommend buying new cutters altogether, and avoiding buying an expensive pair of cutters because they will eventually become dull. But if you want to keep your cutters for whatever reason, you'll need to buy a fine hand file.
Hand files come in sets in different grades that are either coarse or fine. This means that the texture on the file is either large and will make a significant depletion in what it is rubbed on, or that the texture is small (fine).
Fine textured files are for more delicate work and allow for better control Because the area of metal to be sharpened on wire cutters is small, you should use a fine hand file. Both sides of the cutter need to be filed.
Gently rub the file against each blade, being careful not to rub too much or for too long. Too much activity with the file will result in surface area of the blade being removed, which will prevent the cutters from closing (and working) properly.
Taking Care of Your Cutters
Regardless of what you do with them, your cutters will dull over time. You can extend the longevity of the cutters by washing them every time after use.
They can be cleaned with soap and water, or with rubbing alcohol and then dried. You can also use bleach to clean and sterilize them.
If you have sap from trees or plants, or any other sticky substance, you can use WD40 (which is an oil that prevents rust) or lighter fluid to remove it. After you dry your cutters, oil them lightly and then store them until their next use.