The best location to sample is the hose bib at the Well Head.
The goal is to sample fresh water from the Well.
Water from the surge tank will have a lower radon level because the radon gas in the water has started to escape.
Run the water until you hear the well pump operate; attach the water fill tool to the hose bib and then fill the sample bottle completely to the top, the water should overflows the bottle. See Drawing
Apply the cap to the bottle.
Bring the bottle to the office on the same day if at all possible.