We love, love, love razor clams and grilled fresh sardines - we had amazing versions of both on our trip to Spain last year and ever since, are always on the lookout for them on restaurant menus. Both sardines and razor clams can be cooked on a grill or a la plancha, or just in a pan or
cast iron skillet 
and served simply with a little parsley, garlic shallot butter sauce or olive oil, and lemons and they are so good! Razor clams are also big in Chinese seafood cooking, typically stir fried with black bean sauce - also delicious. We were excited to see them at the fish vendors on Grand St. in Chinatown this morning and bought a pound, which gave us 13 clams. We also bought a few fresh sardines, and made a nice, simple lunch of razor clams and sardines with a little garlic and shallot butter sauce, parsley and lemon juice, and served them with a little bread. Not only are sardines sustainable and low on the food chain, but they really are delicious and I hope you'll give them a try sometime- canned sardines can be great (try eating the ones in tomato sauce with a little rice sometime - an easy and tasty dinner!), but fresh sardines are really a whole different thing - so good just really simply seasoned. If you're a little squeamish about whole fish, or fish with bones, take baby steps and soon enough, you'll get past it :)
Razor clams
It was hard to figure out how to clean them since everything online seems geared at Pacific razor clams that are rounder and more clam shaped. The Atlantic razor clams have 5-6" long, dark, mostly straight shells a little less than an inch thick. So, I texted a friend and my sister who cook professionally, and they both said to cut off the siphon end (it'll be the opposite end of what you see sticking out here - don't worry, you'll be able to tell which end is the siphon end), and my sister said I could probably soak them in a little salt water for a while to get them to spit out their grit a little. So, we did, and I think it helped because they were pretty much grit-free. We had them at a great restaurant once where they were super gritty so we were definitely a little hesitant about trying to cook them ourselves.
We heated up our cast iron skillet with a little olive oil and got it really hot and tossed them in. After they all popped open, we pulled them out and trimmed off the siphon end. We had made a little garlic and shallot butter sauce (melt some butter in a small sauce pan and add some minced garlic and finely chopped shallots, a little salt, and cook until the garlic and shallots are tender) and drizzled that over the clams, squeezed a little lemon and sprinkled them with some chopped parsley.
Grilled or pan-seared fresh sardines

If the sardines aren't sold already cleaned, as you'll probably find them in Chinatown, look for the freshest ones with the clearest eyes and without any blemishes or tears anywhere - they're easy to bruise up. When you get them home, run a small knife gently along them from tail to head to scrape off the scales - their scales come off very easily - until they feel pretty smooth and free of any scales. Don't worry too much about scales on the head as you probably won't get much from it anyway. Very gently, remove the little fins along the stomach and along the top of the fish - hold the fish and gently twist and pull them off. Be really gentle along the stomach or you could end up ripping it open. With your knife, cut gently and cleanly along the bottom of the fish. Just run your finger along the inside to pull out the insides - it's not as awful as it sounds and is pretty easy. Give them a good rinse under running water.
Dry them off with a paper towels, drizzle with a little olive oil and salt, and then add them to a hot cast iron skillet or griddle, or if you have a grill, go ahead and throw them on a grill - make sure you oil the grates well so they don't stick. We don't have one, so after cooking the razor clams, we then cleaned out the cast iron skillet a bit, heated up a little olive oil, and cooked up the sardines. Cook them for a few minutes, maybe 2, on each side, and then you can also drizzle a little of the garlic butter sauce, or just a good olive oil, squeeze some lemon juice over them and sprinkle chopped parsley and a little
fleur de sel
or sea salt on top. There meat on the top half (horizontally) of the fish will be easy to remove with your fork and get off the skeleton or bones. The bottom half of the fish have softer, longer bones that run around the stomach cavity. You can pull these out, but they'll most likely be soft enough to just eat without much notice.