Few Greek restaurants seem to get everything right; you'd do best to pick your favorite by their specialty. At E Taverna in Astoria, it's molluscs.
The Htapodi Sharas ($14, charcoal-grilled octopus), may be the most tender, flavorful, and smoky I've had anywhere, Greek-style or otherwise. Thick slices of octopus tentacles are grilled until just soft, then washed in good olive oil and tossed with a fistful of capers along with some of their juice. It looks like too much brine, enough to sail right over the octopus's gentle sweetness, until you taste just how rich the meat is with all that olive oil. The tentacles are so tender you barely need to chew them, crisped just-so with some char that adds a smoky character to the dish. Consider placing a second order once the first hits the table.
E Taverna also nails Mydia Saganaki ($9), mussels steamed with tomato sauce, wine, and cheese. As with the octopus, the mussels are gorgeously tender, as plump and juicy as raw oysters, and they stand out against the bright, sweet, and salty flavors of the sauces and cheese they're served with.
There are salads, dips, and cooked vegetables to round out your meal, and from what I've tasted so far they range from just okay to homey-nice, but you wouldn't be wrong to make a meal of octopus, mussels, and the restaurant's great bread, ordering seconds and thirds as needed.