The fact that there are two is a red herring - you only need one of them. Ask either of them the question:

"If I ask you if the left fork leads to Someplaceorother, will you answer 'yes'?"

If the person asked is a truthteller, he will answer "yes" if the left fork leads to Someplaceorother, and "no" otherwise. But so will the liar. So, either way, go left if the answer is "yes", and right otherwise.

It is possible, of course, that the liars are malicious, and they will tell the truth if they figure out that you are trying to trick them.

If you just want to identify which is which, ask either one some question like "Is one plus one equal to two?" The truthteller will answer "yes," and the liar will answer "no," and you can figure out the identity of the other man by process of elimination.