Better ways to use DJ landmarks You can mark introductions, verses, choruses, and other key parts of a song's structure. You can mark when the voices start. You can try out interesting parts of a song. You can skip parts of a song.
You can mark the key starting points of a song. You can mark the key endpoints of a song. In all cases, always place a reference point at the beginning of a bar or phrase. Matching the bars and sentence structure is critical for a smooth mix.
You can learn more about song structure in this handy guide. The purpose of the initial reference points is to establish good points to start mixing on a track, as well as to mark the first major changes to the track.