Cruising around the mountain on your fresh-out-the-pack board with shiny new edges is all fine and dandy but eventually after inevitable wear and tear you’ll find your edges aren’t the same as when they first started out. Gently rub your thumb along each edge. If they feel dull, rounded or burred, it’s time to sharpen them.
For this you will need a proper ski or snowboard edging tool. This has a built-in guide enabling you to maintain the correct angle.