Keeping your skis properly tuned is an important part of maintaining their performance. While some things, like a stone grind, can only be done by a professional shop, a lot of upkeep tuning work can be done at home with some simple gear. Additionally, keeping a slopeside tuning kit with you when skiing can help you touch up the skis if anything needs to be done while riding.
Keep your edges sharp, as they are critical to your ability to carve a turn on hardpack snow. Run your fingers lightly along the edges to find find any burrs or deformations. Use a diamond stone, placed in an edge guide, to smooth out the burrs on the edges. After removing burrs, sharpen the edges using a standard file. Use an edge bevel guide and attach the file to it with clamps so you don't over-file the ski edge and ruin the correct angle. Use a portable edge bevel guide with a simple file that is included with it to do quick edge filing at the slopes.
Check the bases for core shots (holes that reveal the core of the ski) and other damage. Significant damage will require professional repair, but a P-tex candle can be used to fill in small divots in the ski bases. Hold a flame to the candle and drip P-tex into the hole, and use a plastic scraper to smooth it out into the hole and over the base. Allow the P-tex to cool, and remove any excess with the plastic scraper.
The art of waxing inspires passionate debate among skiers and racers. Hardcore skiers will wax their skis every time they hit the slopes, trying to match the ideal temperature wax to the snow conditions they expect to find. If that seems like too much work, err on the side of waxing for too cold a temperature instead of too warm a temperature. Using a warm temperature wax on cold snow will make the skis feel like they have a layer of sandpaper on the base.
Carry a crayon-on wax with you to the slopes and renew the layer by quickly crayoning on a thin layer of wax to the base if you feel the skis are dragging or sticking.
For home waxing, invest in a waxing iron, which will melt the wax at an even temperature and not scorch it the way a clothes iron can. A good technique for hot waxing is to crayon the wax onto the ski, then use the iron to melt it into the bases. Allow the wax to cool for 24 hours, and use a plastic scraper to remove any excess.