The first thing I do with any silver necklace is hold it up to the light and check the clasp, because that little lobster claw is the part that always goes first. If it feels stiff or fiddly with one hand, that's how it'll be every single morning, rushing out the door with wet hair. A good clasp should open smooth and close with a proper click you can hear.
Silver isn't the right choice for everything, and I'll say that plainly. If you're near water a lot, swimming, hot tubs, the sea, it'll dull quicker than you'd like, and you'll end up polishing it more than wearing it. It also sits oddly against very warm, golden skin tones sometimes, going a bit flat rather than bright. And if you want something you never think about, that just stays shiny with zero effort, silver asks a bit more of you than that.
Before you buy, check the weight of the chain against what you'll actually hang on it. A fine curb chain can look lovely empty but sag or kink under even a small pendant. Look at how the pendant sits too, does it face forward properly or does it flip round and show the back of the chain. Run your fingers along any chain links to feel for rough edges, because that's often where plating or finish wears thin first and where it catches on jumpers.
On finish, I'd always go for something with a slightly brushed or matte texture over anything too polished and mirror bright. The high shine shows every scratch and fingerprint within a week, whereas a softer finish hides the small marks of actual wear. Sterling silver that's gone through proper hallmarking tends to hold its colour better over time too, rather than greying out at the edges. A pale, cool silver works with almost anything in a normal wardrobe, grey marl jumpers, white shirts, denim, black coats, it doesn't fight with colour the way gold sometimes can against certain reds or oranges.
For actual outfits, I wear mine with a plain white t shirt and jeans most days, nothing clever about it, and it's the one bit of jewellery that still looks finished when everything else is thrown on. Layered under a crew neck jumper with just the pendant showing is another easy one, especially useful on days you can't be bothered with earrings too. A longer silver chain over a simple black dress does more for an evening than people expect from one thin piece of metal.
Let the chain length sit just above where your neckline starts, that's usually the length that looks intentional rather than accidental.