Commercial dredging
Commercial fishermen use dredgers to harvest clams from the sea bed. Another technique for commercial fishermen is to use clam tongs or a clam rake from their boats to catch the clams and then put them in baskets. Environmentalists favor manual methods of catching clams because over-rigorous dredging in large quantities can damage the sea bed.
Digging
If you want to dig for clams you need to equip yourself with a shovel or a simple hand rake. A gardener's rake or potato rake will suffice. You need something with prongs so that you can use the fork in an up-and-down motion to disturb the sand and find the clams. However, it is important not to be too vigorous or you could break the clam shell. Razor clam shells are sharp, so dig slowly and carefully if any of that species are around. Wading and digging with your hands is another effective technique if you do not possess a shovel or rake.
Cylindrical gun/tube
Using a clam gun is efficient but can be heavy work in terms of lifting the gun with the sand inside. Place the gun over the "show" (small, round blobs) indicating there are clams under the sand. Push the gun straight down and then cover the air hole with your finger. Pull out the gun gradually with the sand inside the gun. Once you have shaken out the sand you should be left with some tasty clams.
Considerations
Check the laws in your state regarding clam catching. For instance, Oregon's Department of Fish and Wildlife requires you to have a license to catch clams and also has restrictions on how many clams you can catch. The state department also sets out the type of cylindrical gun that can be used to catch clams. Other considerations when catching clams concern safety: some clam pickers have died when the tide has come in so make sure you check the tidal information carefully. Dress appropriately for the task as the environment for clam catching can be wet and muddy. Waders are a sensible idea.