My first clue of a bad photograph is when I look at my still wet negatives and say to myself "What was I thinking!?" I have revisited old negatives and found images which seem better after a period of time. I've heard of photographers who will wait awhile before developing their film so the excitement they felt when shooting the image has worn away by the time they see the result. Supposedly it makes for better editing (and possibly avoids huge letdowns as would be my case).