A good lace top has a bit of weight to it before you even get it over your head. Not stiff, but enough body that it doesn't collapse into itself in the bag. Cheap lace feels like a doily that's given up. The decent stuff has a proper scalloped edge you can feel with a thumb, and the lining underneath sits separate from the lace rather than being the same bit of fabric with holes punched in it.
Worn over months, lace either gets better or gets sad, there's no middle ground. The good ones soften at the seams and the pattern stays crisp because the thread's tight enough not to snag on a bag strap or a bra clasp. Hand wash if you can face it, cool machine wash in a bag if you can't, and never tumble dry, the elastic in the trim gives up and the whole thing goes a bit limp and apologetic. I've got one that's three years old and still holds its shape because I've never once put it near a radiator to dry it faster.
What it doesn't want is noise underneath or beside it. A patterned bra showing through white lace is a look, but not the one you wanted, so go nude or match the colour as close as you can. Skip chunky statement necklaces, the lace is already doing the detail, and anything else heavy round the neck just competes with it. I'd also leave it out of anything that needs to look sharp and corporate, lace reads soft and a bit romantic even when it's black, so it sits better with jeans or a plain skirt than it does under a blazer trying to be serious.
In the shop, check the side seams and underarms first, because that's where cheap lace tends to pull and show gaping you won't notice until you lift an arm on a bus. Hold it up to the light and look for the lining showing through in patches it shouldn't. And check the trim round the neck and cuffs isn't just lace left raw, it should be finished or backed with something, otherwise it curls after one wash and never sits flat again.
Look at how it sits under the arm before anything else, that's where you'll know in two seconds if it's been made for a real body or just a mannequin.