You should post this question under ADVICE>Home Forums>Plumbing. In general, you should start by locating your water meter which is usually in the right of way near the street. The pipeline usually follows a straight line to the house and often lines up with an outside hose bib. A crawl space or basement makes it easier to find where the pipe enters the house as the pipe will be the only one coming up out of the ground. The exception to the straight line route is if the land has large boulders or mature trees that necessitated a detour. The water line depth will be based on how deep your soil freezes, but probably a minimum of 18 inches.

mindshift, thank you for the advice. I didn't even think to look for a "plumbing" section.

We had good luck finding ours with dowsing rods dh made. Some are skeptical, but it's worth a try. Beats $800.

I agree on the dowsing rods. Sometimes you even find some artifacts buried in the ground also.

I was going to suggest dowsing rods as well. I just use a couple of pieces of bare copper wire bent and put in a couple short pieces of 1/2" PVC pipe. It doesn't work for everybody but it works great for me. I have found water lines, buried electric lines, sewer lines, etc... Whenever I cross a line the wires will cross each other and line up with the direction of the line. It is funny my friend will go over the exact same spot and find the line in the same spot but the wires will turn out away from each other. It seems to act different for different people. I would give it a try. It can't hurt and you might be surprised.