There's a particular kind of evening, kitchen lit up, something simmering, someone leaning on the counter talking to you while you cook, where your hand is on a cabinet pull a dozen times without thinking about it. That's when you notice whether it feels solid or whether it wobbles a little in its hole and makes a tiny metallic click every time. You don't think about handles until that moment, and then you think about nothing else.
The difference between a good one and a bad one is mostly in the hand, not the eye. Solid brass, bronze, or stainless steel has a certain weight and a cool, dense feel, and the finish is usually plated or coated in a way that resists the oil from your fingers for years. Cheap pulls are often a lighter alloy with a thin finish sprayed on top, and that finish wears through at the exact point your thumb lands, so within a year you have a bright little scuff mark on every single handle in the kitchen, all in the same spot, like the cabinets are tattling on you. Check how the pull attaches too. Good ones have a solid, threaded post and a backplate or base that sits flush with no gap. Bad ones have a thin screw that strips if you look at it wrong.
Sizing is where most people guess and get it slightly wrong. Measure the width of your drawer or door face, not the whole cabinet, and keep pulls roughly proportional to that, generally a third to half the width on drawers, with knobs reserved for narrower cabinet doors where a bar pull would look stretched and awkward. Hole spacing matters more than people expect, since most pulls are sold by the center to center distance between screw holes, and if you buy a new style with different spacing you'll either need to drill new holes or buy a backplate to cover the old ones. Measure twice, then measure the actual screws you have, because some drawer fronts are thinner than they look and a long screw will poke straight through the front and into your spaghetti.
Where they don't belong is anywhere too ornate next to very plain, flat panel cabinets, since an elaborate pull on a simple door reads like a wedding ring on a gym sock. They also fight with handles on appliances right next to them if the finishes don't match even loosely.
They won't fix bad cabinet boxes, hinges, or a door that doesn't sit straight, so don't expect hardware to rescue construction problems underneath.
Change them out on a kitchen you already love and the whole room suddenly looks finished, like it was always meant to look that way.