If I am running underground wiring and using a GFI circuit how far down does the wire need to be buried and if its specific underground wire does it need to be in a conduit pipe through out the run or just at the point coming out of the ground to the outlet box. This is a 110 volt 20 amp circuit:

A conduit or direct burial UF cable can be at least 12 " deep, if the circuit is residential, no more than 20 amps, and GFI protected.

This means using a GFI breaker to protect the entire circuit, not just a GFI receptacle.

If you don't want to use a GFI breaker, then UF cable needs to be 24" deep, steel rigid conduit 6" deep, or PVC conduit 18" deep.