Genealogical Research Standards by Derek Harland

This is an older book but still quite good. The audience is primarily those using the LDS Church resources circa 1963, but the general ways and methods are quite modern. I am reminded of the current Genealogical Proof Standard requirements laid out in other books more recently published.

You can find copies of this book through Bookfinder.com or Used.Addall.com for between 6 and 10 USD with shipping.