Start by hitting a bunch of shots with your feet dug in deep to the sand. Notice how heavy it feels and pay close attention to the height, spin, roll and overall result. This is a great play if you need the ball to hit and release on the green.
Next, dig in less and again pay close attention to the result. You should see higher shots that land softer on the greens and check up much quicker. Note that to dig less you also need to make sure that you are setting your club face more open to utilize the bounce on the back of the club head.
By practicing the Foot Depth Drill, the depth at which you dig your feet into the sand will help you determine the amount of sand you need to take and what type of splash you will make, how high or low the ball will come out and how much spin will be on the ball. When you dig in deep you will hit down deeper taking more sand. The ball will tend to come out lower, hotter and with less spin. When you dig in less, you will smack the top of the sand making less of a splash. The ball will come out higher and with more spin.