Ski and snowboard edging tip - Use a marker
A good ski sharpening tip to remember is to run a magic marker down the edge of the ski/snowboard before you begin to file. When you file the mark off you can be sure you are close to finishing that part of the edge, and you will know where to start your next stroke.
Make your file strokes in lengths that don't strain your arm by pulling the tool 16-18 inches, then overlapping. Always file in the same direction - from tip to tail.
File in the same direction - Tip to tail
You can get a ski/snowboard angle file from your local snow shop. These files have the angles preset, so you won't blunt your edges which is possible using a conventional file!
If the file feels like it is not cutting, clean off the file with a wire brush or adjust it in the bevel tool to a new spot. If it is still not cutting get a new file. Test the sharpness of the edge of your file by rubbing a fingernail gently across the edge. A finished sharp edge will remove a visible wrap of your nail, while a dull edge will not.
Fine-tuning your skis and/or snowboard
Once both edges of a ski/snowboard are done, run a fine diamond stone or piece of fine bit of sandpaper (emery paper) over the edge.