I sharpen my hooks to a diamond or triangulated point so that there are cutting edges to help the point penetrate. For this reason, soft sharpening stones are not good; they tend to groove when used and won't produce that sharp, cutting edge. A 6-inch Nicholson smooth file works well and is widely available at many hardware stores. Any file that is coarser than one designated as smooth is often too rough to get a nice cutting edge, especially on smaller hooks. What is even better is a 6-inch file with a No. 4 cut. This file has even finer teeth than the smooth style, but is sometimes difficult to obtain. I buy them from a machinist friend and use them to create my primary hook points. Then to touch it up, I use a file that has a coating of diamond dust. Such a file won't rust and is great to keep in the boat.