I think part of what to do depends on where the picture came from. Did someone give you a snapshot and say "print this", or is this from a serious photographer that already did a lot of post processing, knows what he's doing, and truly wants the picture to be as given to you?
If the unsophisticaed customer case, then part of the solution is to fix the low contrast snapshot to use the full dynamic range and therefore have higher contrast. For example, here is the original:
and here is a version with the lightest and darkest parts expanded to be full black and full white:
Personally, I like the second picture better as it is much more dramatic and interesting to look at. In the case of the unsophisticated customer, this might be what they expect you to produce. Of course if someone that thought about it and really wants the dark and dreary mood of the first picture, then you need to preserve it. Even in the first case, a conversation with the customer is in order.