This isn’t, technically, a mystery, but still pretty much sounds as if it belongs on this blog anyway!
How to Solve a Cold Case: And Everything Else You Wanted To Know About Catching Killers, by Michael Arntfield, seems to be, per its blurb, pretty much what the title says it is. And it seems as if Arntfield, who is a former police detective, and currently the Director of the Murder Accountability Project in the United States, and the founder and Director of the Western University Cold Case Society in Canada, should know what he is talking about. And How to Solve is on sale right now for $2.99 in US.