Empty shells are a collector's fair game on any beach. Many species, like the angel's wing, are fragile and must be handled accordingly. Take along a number of instant coffee jars with lids so that you can half-fill them with seawater to take home brittle or live shells.
Goggles, a snorkel and mask, or a glass-bottomed box without a lid, are prerequisites to looking for live shells underwater. Some boxes are custommade, but a number of other objects can be put to use - like a cube of eighth-inch lucite designed to hold kitchen implements.
The American Malacological Union's handbook describes a complete kit and outlines a code of ethics for shell collectors. Two major items: don't take endangered species home; and, if you turn over underwater rocks, put them back in place rightside up. It takes considerable time for algae to grow on their exposed surfaces.
A plain old tire iron (the one-socket kind) is useful for prying up rocks or certain crustacea. Tie it to your belt with some light line because it'll sink. A garden trowel or folding GI shovel is useful for digging in sand. Crab nets or baited lines are a must to catch crabs. A pocket magnifying glass is an eye-opener for examining small plants, animals and simple seawater which is alive with complex tiny things.
At the other end of the spectrum, binoculars are useful to study a number of critters. Most of the birds are simply too skittish to stand still while you walk up close enough for a good naked-eye look. Glasses are also useful in observing sand hoppers, ghost crabs and the like, and small animals ten feet away.
Do not take sprigs of plants - especially sea oats and beach grass. Berries and the like are legal (though the beach and its denizens really need the vegetation more than you do).
The general rule on federal beaches is that you can take anything dead or inanimate in moderate quantities, i.e., armfuls of empty whelks and driftwood. Commercial collectors are discouraged.
You may also take all the living shellfish you can dig up, except on leased or private grounds which are often marked with plain stakes.
Do not attempt to take any live land vertebrates home, avian or mammal. For one reason, they're wild animals and are very likely to hurt you if you insist on getting too close. This goes for raccoons, moles and Assateague ponies.
Do not disturb nesting birds! Watch them through binoculars and enjoy.