For most of us, walking into a seafood store is an exercise in both ignorance and hope: we’re ignorant of what’s available but we hope we’ll leave with what we want. We all know fish come in two colors: the red one is salmon and the rest are white. Here is what you should know about fish:

Mark Musatto, a partner at Airline Seafood in Houston, says “There are three basic feelings I want every customer to have when they enter my store: they should feel, smell and see the freshness; notice that fresh fish has a sheen and a translucency and I want customers to tell me how they plan to cook their fish and we can talk about the best fish for that method.

“Some fish are better for grilling, others for sautéing, and others for frying.”

There are some basics to consider and ask about when you shop for fish:

• Do you know the store to be safe and reputable?

• Is the seafood fresh or “previously frozen”?

• Where was it caught — Is it local or shipped in from afar?

• How was it caught — is it from open waters or farm-raised?

• And, the increasingly vital question: Is the store selling varieties of seafood that are endangered?

A seafood store must have some basics that make it a good, safe place to shop. The smell should be clean, not too “fishy”; there should be constant filleting of fish so the fish is always fresh, not dry or brown from exposure to the air; fish must be left on the bone as long as possible and those handling the fish should be able to answer any questions you have.

A question to help separate the average shop from the superior one: Is this a store where restaurants buy their seafood? The answer must be “yes.”

How to tread lightly when dining on seafood

The word “seafood” doesn’t define only fish. Seafood includes scallops, lobster, oysters, clams, mussels, crawfish, crab, shrimp and other non-fish creatures. And among these are endangered varieties.

The Environmental Defense Fund has put together a Seafood Selector (available as a pocket guide) that will tell you everything you want or need to know about the status of fish and seafood stocks around the world. They have grouped seafood into three categories: Eco-Best, Eco-OK and Eco-Worst. But there is always a dispute among fishermen, governments and private organizations about which varieties of seafood fall into which category. And restaurants don’t always abide by the warnings about over-fished species.

For example, Chilean Sea Bass is on just about every Eco-Worst list but it’s still on many menus. Bluefin Tuna, the staple of sushi, is also on that list but every sushi bar in the world serves it.

Some Salmon are endangered, some not. Some trout are threatened, others not. Ask your fish-seller and your restaurant waiter if you have any doubts or questions. Don’t fall for something that is out of season (”wild” Alaska Salmon in winter) or is a substitute for the real deal (farmed White Bass or Catfish for Grouper).

(Note: Chilean Sea Bass, Bluefin Tuna and Atlantic Salmon are all considered in jeopardy, and they’re fish that tend to carry high mercury concentrations, so staying away from these varieties provides a double benefit.)