Get a mill bastard file or a small bench grinder. Most folks will tell you not to use a bench grinder, saying that it can heat up the pick and ruin its temper, but if you go slow, touching the pick for just a second at a time and immediately cool the pick in a cup of water, a bench grinder is the most precise.
Either way, you’ll want to sharpen your pick after almost every outing. A razor-sharp pick requires less energy to stick into the ice, fractures the ice less and yields a more secure placement. What’s not to like? To sharpen, file the end of the pick following the manufacturer’s bevel. Hone it until all the dull metal shines and the edge is knife sharp.
If you are sharpening a mountaineering axe, you are done. But, if you are touching up a ice or mixed tool, you have work ahead. If the topside of the pick is beveled, file it until it is as sharp as the end of the pick. Filing here will reduce ice displacement and fracturing, let the pick knife in more easily, and make it easier to clean the tool by rocking it up and down in the ice.
Sharpening and/or modifying the underside of the pick is the trickiest bit, but the one that can improve performance the most. For ice climbing, simply bevel the sides of the teeth following the factory grind. For mixed, do the same, then pay attention to the tooth just behind the tip of the pick. Some climbers like to file this first tooth completely away, then undercut right behind the tip of the pick with a round file until it resembles a cat’s claw. This shape is the best for hooking rock. It is the worst for pick longevity as it dulls quickly and can’t take many resharpenings, a consideration when picks cost $40 or more a piece. If you will only dry tool on occasion, or don’t care for maximum performance, keep the first tooth, but file it down so it doesn’t hang lower than the tip–a too-long first tooth will lever your pick off its purchase.