I like having to cope with moral dilemmas in RPGs, so <img src="/ubbthreads/images/graemlins/up.gif" alt="" /> <img src="/ubbthreads/images/graemlins/smile.gif" alt="" />
Of course, the player should have some general idea of what his character's actions will lead to, else you might get the impression that you can't really influence what happens, and that might cause frustration. On the other hand, that's how it is in life: you can't always tell what you'll get when you act in a certain way.
Providing some sources of information that are easily available, e.g. by talking to people or by reading books, should be enough to let the player guess what will happen most of the time, but there should also be some liars or erroneous texts that prevent you from knowing exactly which long-term consequences your actions will have. And please don't make it too obvious when people are lying.
For those who always want to make the right decision, there could be a divination skill that grants visions of the possible consequences, maybe a short cut-scene that will illustrate what could happen if you choose this or that option.
