If there's one thing I wish I could change about the American diet, it's how we eat fish. First, I wish we ate more of it—while keeping an eye on making sustainable choices. And eating more of it means cooking more of it at home. Second, I wish we branched out to fish beyond the over-consumed salmon, shrimp, and tuna, because our waters hold a lot more than just those three creatures. (Plus, I'm pretty sure there's a heck of a lot of salmon, shrimp, and tuna out there that would thank us for laying off just a little bit.)
The thing with fish is that it continues to intimidate people, both in terms of how to shop for it and how to cook it. The sustainability issue doesn't help bolster consumer confidence much either, but the good news is that, at least in New York City, there are new fishmongers popping up that are doing an amazing job of bringing responsibly caught fish to their counters, and even some of the big boys are doing an admirable job. (In fact, Greenpeace just released its 2014 list of the most sustainable seafood retailers, and Whole Foods, Safeway, Wegmans, and Trader Joe's all scored very well: I encourage everyone to read through Greenpeace's report, and keep it in mind the next time you're trying to decide where to buy fish.)
One of the best solutions to this intimidation factor is to buy whole fish. I know, with their heads and fins and tails, that may sound counter-intuitive, but there's a reason: It's much easier to judge the freshness of whole fish than fillets or steaks.
Why? Well, first you can look at the eyes, and see how clear and plump they are. Clear and plump equals fresh; cloudy and starting to dry and collapse, not so much. Second, you can check the gills: They should look wet and a lively red/orange/brown color, not dried or dark brown. Third, you can gently press the fish's flesh to see how well it springs back—if you leave a dent that doesn't recover at all, move along.
As for smell, a whole fish will smell like a fish, of course, but it should smell like a fish that's been recently plucked from pristine marine or fresh waters. If it's starting to stink a little, that's not a good sign.
And cooking it is just as easy. Ask your fishmonger to gut, trim, and scale the fish—there's no reason to complicate your life with tasks like that. When you get home, give the fish a soak in salt water (I learned that trick from a sushi chef I chatted up once while eating omakase at his bar), pat it dry, and season it inside and out with salt and pepper, just as you would a chicken.
Then stuff some aromatics into the cavity. I like to use fresh herbs like parsley and oregano, along with cloves of garlic, and slices of ginger and lemon, but really you can use anything that will add flavor to the fish. Give the fish a little rub down with oil, transfer it to a rimmed baking sheet (I like to line the sheet with parchment for easier cleanup later), and roast it until a thermometer inserted into the thickest part of the fish reads about 135°F. (Other ways to judge doneness: The fins should come right off when you pull them, and you should be able to feel the fish flake slightly under the skin when you press on it.)
As for serving sizes, a good rule of thumb is about 1 pound of whole fish per person, so you could do individual 1-pound fish, or split a 2-pounder between two people, and so on.
Carve the fish following this easy guide, and serve.