Though I don't really understand idea behind the the "From a PJ perspective" part of the question, this is what I think. From a photojournalists perspective, the best possible UFO photo would be one that was widely witnessed and/or photographed and/or reported by others, and that was backed up by scientific evidence to lend your story some real validity.
Technically speaking, a photo that was perfectly technically sound and had lots of detail would help. UFO photos never are.
...but really, these are all only considerations for people with any brains. All you really need is a bunch of idiots as an audience to be taken as credible.
I would look into the techniques employed by Jerry Uelsmann. Printing from multiple negs, masking, etc. Fun and challenging stuff to try to pull off.