Just an added point of information to LapLap's excellent advice: Takao San Guchi Station is on the Keio Line out of Shinjuku. There is a Takao Station on the JR Chuo Line, but it's not very close to the mountain, and you have to transfer to the Keio Line there anyway, so unless money is tight and you have a JR Pass that you want to make the most of, just take the Keio Line all the way.