Oh boy, there's so much that can be said about that one.
In general, the barrel should be free floating, except right under the chamber / knox, and under the front sight. At that spot (front sight), there should be upward pressure of... is it between 3 and 7 pounds? Then, there should be contact between the forend and the bottom face of the receiver, and between the front face of the butt socket and the rear face of the forend. I think P. Laidlerexplained it best to me about a year ago, I'll try to see if I can find that reference. And someone (Ed?) had a great picture that showed where the contact surfaces should be...
Oh and the sear lugs should also put pressure forward on the forend.
Lou