PSU kit has directions on the formsI think the OP want to know how you do a soil test. I maybe wrong.
Here is how I do it. I take a small hand held shovel and dig down about 4 to 6 inches and dump it in a clean bucket. I get 5 samples from each plot.
I do all four corners and one from the center. After mixing altogether i place a small sample into a plastic zip lock bag and then I drop them off at Agway.