Good seafood tends to give itself away with a smell, actually — the ocean, maybe a little brine, never that heavy "fishy" odor people associate with old catch. Eyes on a whole fish should be clear and a bit bulging, not cloudy or sunken. Press the flesh gently; it should spring right back instead of leaving a dent behind. Gills matter too, and they're easy to check — red or pink means fresh, grayish-brown means it's been sitting a while. Worth asking around at a good fish market, since staff usually know the delivery schedule better than any label would tell you. Shrimp should look almost see-through, not chalky or opaque. And with clams or mussels, closed shells are the rule until heat opens them up. Honestly, if something smells or looks slightly wrong, that instinct's rarely lying to you.