Find an area to build your sand castle. It is recommended to build the castle where the sand is wet, but not too far away from where the waves wash up on shore. Level out a pad of wet sand with your hand. The pad should be slightly bigger than your sand castle will be.
Scoop some wet sand into a bucket. Fill it up almost to the top, and make sure it is packed in tight. Turn it upside down on your smooth patch of wet sand. With one hand, tap the bottom of the bucket, and with the other, hold the bucket still. Lift the bucket up. The wet sand inside should have taken shape of the bucket. The wetter the sand the better.
Repeat step 2 as many times as you desire. Try to arrange the castles in a sort of shape.
Collect some shells. Stick them on your castle for decoration.
With your shovel, dig a moat around the castles. Pad the sand in the moat very tightly. Get your bucket and collect some seawater. Pour the seawater in the moat.
Collect some Sand crabs. You can find sand crabs by digging a hole in the sand at the very edge of the wash from the waves. Allow water to enter the hole, and swish it around. You should see sand crabs darting through the water before they quickly bury themselves in the sand. These crabs will be the people in your castle. They dig though, so you will have to pad the sand around your castle very tightly so they don't escape.