I found the best policy was to forge the previous captain's signature.
If it is just the signature that is missing its by far the easiest solution to the problem and one I have used on several occasions, on our company paperwork there is always a previous page with the pre-departure signature on it so its not too hard.
The problem, and one that does require contact with the previous skipper or an engineer to sort, is if the technical state (new defect or nil further) has not been recorded.