The first cut in the spring and the last cut in the fall should be low. In the spring this removes any winter fungus and in the fall prevents fungus from getting established during the winter.
When using hand files, it is best to hold the stock firmly in a vise or clamp. For better results, try to keep the stock being filed at about elbow height. For heavier filing work, the stock should be lower; if the work is finer, try to keep it up closer to eye level.