[joaquimandrade]

I think this question would work:

What is the path that the other fellow will tell me to follow if I ask him whats the best path?

The truthful one would tell the bad path because the other one would lie.
The liar would tell the bad path because he would lie about the truthful one choice that would be the best.

So you would know the bad path and therefore the good path too.

Edit:

Ade already provided the answer

[ConnorMcLeod]

But what if the truthful one doesn't know that the liar is a liar (and vice versa) ?

[ajr1234]

Originally Posted by ConnorMcLeod But what if the truthful one doesn't know that the liar is a liar (and vice versa) ?

Precisely.

The liar might not have been to Hell either. If he knows what the other guy will say, then he's lying, because a liar can't tell if the other guy is lying or telling the truth.

[XINLEI]

no matter what question you do, you have an 1/4 chance to get the right answer.

[Powerlord]

Originally Posted by XINLEI no matter what question you do, you have an 1/4 chance to get the right answer.

True, but like previously mentioned, if you ask what the other one would say, you'll always get the wrong answer. Which means you just choose whichever one they don't tell you.

Also, a variation of this particular mystery was in the movie Labyrinth.

[ajr1234]

In post 5, I thought of an alternate solution.

Originally Posted by ajr1234 Perhaps you can ask a question dissimilar to the problem at hand. "How is the weather like in each direction?" The truthful man will point to heaven and describe a wonderful sunshine and calming breezes, and then point to hell and say, "I do not know the weather at this direction because I cannot go there." The liar would point to heaven and describe a terrible storm, and then point to hell and describe serenity. You know immediately that each man can only belong to one track and not both, and thus cannot know the status of both tracks. The liar cannot step foot in heaven and thus cannot know the weather in heaven. The track suggested is accurate if and only if one response does not completely answer the question, in which case that response is correct.