Hold it up against yourself before you buy it, not just on the hanger. A leather skirt should sit at the waist or just below, with enough weight in the fabric that it doesn't cling to every seam of your tights underneath. If it feels stiff at the till, it will loosen with wear, that's normal, but if it's already creasing oddly across the front in the changing room, it's going to do that every time you sit down for the rest of its life. The ones that work best are a straight pencil shape or a gentle a line, something that skims rather than hugs, because the material does enough visual work on its own without the cut adding drama too.
This is not a skirt for sitting on a bike, for a long train journey where you'll be folded into a seat for an hour, or for anywhere with a lot of standing around in heat, leather does not breathe and you will feel it by mid afternoon. It also struggles in the rain, not ruined exactly, but you'll spend the walk home worrying rather than enjoying yourself, so it earns its wear in the colder, drier months, from autumn through to early spring, and it's at its best for evenings out, for a dinner, for the kind of office where smart is encouraged but a suit would be overkill. Pair it with a plain jumper and boots for daytime and it looks like you got dressed on purpose rather than for effect. Pair it with a simple top and bare legs for evening and it does something a cotton skirt never quite manages. What it clashes with is anything else trying to shout as loudly, another leather piece, a heavily sequinned top, a very busy print, all of it fights for attention it should be giving to you. Keep the rest of the outfit plain and let the skirt be the one interesting thing in the room.
Black is the easiest colour by far, it goes with almost everything already in your cupboard and hides the inevitable scuff better than anything pale. Tan and burgundy are close behind, good with cream or navy, and worth it if you already lean warm in your other clothes. Avoid anything with a very high shine unless you like the attention, a matte or slightly worn finish looks more like it belongs to you and less like it just came off a rail. What it will never be is comfortable for a full day on your feet, and no amount of good buying gets around that.