Those who have gone before often leave a path to follow. For many, this is a helpful way to find direction and help in genealogy. Finding this help will save many a hour (or days) in tree climbing experience.
Perhaps it is a family member who has already done most of the work on the family's history. Perhaps it is a writer, or historian, or just plain Sam who loved to climb trees. At any rate it is often helpful to seek this source.
My Dad gave his advice on "Dirty Books".
A path well worn.