I avoided black t-shirts for years, convinced they were the laziest item in anyone's drawer, the sort of thing you reach for when you've given up on getting dressed properly. Then I had a week where three meetings got moved onto camera with two hours' notice, and the black t-shirt under my blazer was the only thing that looked deliberate rather than panicked.
Once I stopped sneering at it, I found it does more quiet lifting than almost anything else I own. Under a blazer it reads as proper office wear, no fuss. With a wide trouser and a flat loafer it does the school run and then a client call without anyone clocking that it's the same top from Tuesday. Tucked into a skirt with a belt it's suddenly an outfit rather than a top, which feels like cheating given how little effort went in. The thing nobody tells you is that black goes with black far more easily than it goes with navy, which always looks like a slightly awkward compromise, the fashion equivalent of two colleagues who've been seated together against their will.
How it wears matters more with black than with any other colour, because fading shows up as a grey cast that no amount of squinting will un-see. A cheap one goes patchy at the armpits and across the shoulders within a couple of months of normal washing, and by week six you've got a top that's black in theory and a sort of murky charcoal in the photograph by the printer. Cold wash, inside out, away from anything with a zip, and skip the tumble dryer if you want it to still look black at Christmas rather than like it's been through a war. A decent cotton with a bit of weight to it holds its colour and its shape for a lot longer than the thin jersey ones that go see through at the first wash and cling in all the wrong places after that.
On fit, the chest and underarm are where it either works or doesn't. Too tight and it pulls across the bust in every photo taken from the side. Too loose and it bags at the front by Wednesday lunchtime and looks like you're wearing someone else's top. Try the arm test before you buy: reach forward as if you're typing, and if the hem rides up past your waistband, put it back.
Check the fabric weight first. Hold it up to the light. If you can see your hand through it, leave it on the rail.