Check the tides before you go, if you are going to get a very low tide it is worth taking a washing up liquid bottle, a spade, a bucket and a load of salt (strong salty solution in the bottle). Get some spouts when the water is at its lowest and eat them fresh with minimal cooking. Great free and easy version of the scallop.
When you see an oval depression near the water line give a wee squirt of the salty water, when the spout comes up dig under it and remove from the sand. Rinse in a bucket for a wee while. Boil water, remove pan from heat, put in half a dozen spouts in their shells and wait for them to open. Remove from shell, cut off guts, eat. A wee pan of butter and garlic to dip them in and some bread is good.
Repeat.
If you look around you will probably get some mussels as well and if you happen to have a collapsible crab pot you may get prawns or crabs to finish your meal.