This is something I've experienced several times, but it was brought home to me most clearly by my most recent question: How can I best deal with the effects of markers with differing levels of generosity in grading student papers?. At present there are two answers that are quite different from one another, and another answer in the comments that is different from either of those two.
My first step is to apply my knowledge as best I can to the answers and try to decide based on that. If that fails I'll often go with the heuristics such as the number of upvotes an answer has received, or whether the answerer is a user I know to be highly reliable.
However, in the absence of those cues, and with a bounty ticking away, I'm unsure how to proceed. Does anyone have any advice?
Relatedly, is there any way for me to see which users have upvoted a particular answer? If so, that could provide another useful cue.