I prefer to use 1/4" Mother of Pearl dots. These are really cheap on EBay and easy to install. The hard part is finding a 1/4" bit that will cut flat on the bottom. I solved this by taking a high speed, strait fluted router bit and flattened the bottom by chucking it into the drill press and using emery paper backed by a steel plate. By slowly lowering the it, the bit sands itself flat on the bottom.
Installing the dots just require setting up a stop on the drill press so the holes are just slightly less deep than the dot is thick. Once drilled and glued in, you sand them flush with fine sandpaper.