Here's a hint: if you're under fifty, you should probably not be writing a memoir. And also probably if you're not Admiral Lord Nelson or someone else actually interesting.
Also, if you're too busy to write a memoir, maybe you should hold off until you're not. You know, in your old age, when writing memoirs is appropriate, and people will mostly read them after you're dead and no longer have opportunities to sully your legacy.
If you've dictated your memoir to a lieutenant as you lie dying in your four-poster, it's acceptable for two names to appear on the cover. Probably, though, your lieutenant will not insist on this, because he has some pietas.
Ghost-written and "co-written" memoirs are fake, pretentious, and a waste of the paper on which they are printed. Shut up, the lot of you.