A good chunk of that answer is gonna be wrapped up in where you're located.
Are you looking to dig a new well? Is it for household use (potable)? For irrigation? For livestock/other animals? Is/was there an existing well? What's the required output in GPM?
It's late so I'm quite tired, but am sure there are more questions that may need to be answered.
"located" or drilled?
As KCM said,,,MANY factors.
I was a tender on IR T4 drilling rigs for years and there are MANY factors to even making sure WHERE you are going to drill has water.
I remember we were in East Berlin area doing a new well for a home owner and we were 100 yards from a very big lake.
Well,,, we went down over 700 feet,, in schist the whole way after 15 feet. He ended up with like 2 gallons a minute.
BUT
On the other hand we were in the diabase in York county and at 125 feet,,,in SOLID diabase,,,the fella hit over 50 GPM.
NEVER take the "first water",,, get down to solid rock and add 50 feet for a reservoir ,,,case n screen it,,drop your pump and you are gold.
DWOLFE, you will have more luck with your question by contacting a good water well dowser. Most of them that I have read about do not charge unless there is a lot of travel expense etc.,etc. I have never been in contact with one but have had a well drilled by pump man. Look for video's on the net and you might get lucky enough to find what you are looking for there.
Good luck, one for me,one for you,one for the road.