It is that moment late on a Sunday when the table has been cleared, the last plate is in the dishwasher, and the living room still has eighteen people's worth of cups and reading glasses scattered across every flat surface. A good tray is what turns that mess into something that looks like it was on purpose. I started keeping one on the coffee table and one on the console by the door, and I noticed the difference within a week. Things stop wandering off. Keys, coasters, the remote nobody can ever find, they all have an address now.
The difference between a tray I keep and one that ends up in the donation pile is mostly in the edges and the bottom. A cheap one has a lip that is too shallow, so glasses slide if the table gets bumped, and a base with no padding, so it scratches whatever it sits on and makes a racket every time someone sets down a mug. The good ones have a proper rim, feel solid when you pick them up with both hands, and the handles, if there are any, are attached with real joints, not glued on and hoping. Wood ones should feel finished on the underside too, not just the top, because an unfinished bottom warps the first time it meets a damp glass. If you have none at all, start with one plain, sturdy tray in a neutral material, wood or a simple metal, about the size of a large dinner plate, and use it on your coffee table for a month before you buy a second. You will quickly find out whether you actually use it for drinks, for mail, for candles, or for nothing, and that tells you what to get next far better than I can from here.
Where they earn a place is the living room coffee table, obviously, but also a bedroom dresser for jewelry and watches, a bathroom counter for the stuff that otherwise ends up in a damp little huddle by the sink, and an entryway table for everything you empty from your pockets walking in the door. A small apartment with one coffee table does better with one good tray than three mediocre ones stacked for show. For scale, measure the surface first: a tray should cover roughly a third to half of a coffee table's top, leaving room to actually put a drink down beside it, not crowd the whole surface so there's nowhere left to rest a foot or a book. On a narrow console, go long and shallow rather than deep, or everything on it looks like it is about to tip into the hallway.
Next to it, I would put a short stack of books with something sitting on top, a candle or a small bowl for the things that have no home at all.