Stand in the aisle and pick one plate up with one hand, the way you would if your hand were wet and your mind was on six other things. If it feels like it might slip, or the rim is so thin you can imagine it chipping against the tap, put it back. You want something with a bit of weight to it, a plate that sounds solid when you set it down on a wood table, not a thin clatter but a dull, settled sound. Check the underside too, run a finger around the foot ring, because that's where glaze pools and bubbles and rough spots show up, and that's the part that'll scratch your table over time if it's not finished properly.
When you're measuring, think about your cabinet before you think about the table. I've bought plates that looked completely reasonable in a shop and then discovered they were a full inch too wide for the shelf, so they sat on their sides, slightly tilted, for a year like they were sulking about it. Measure the shelf depth and height with the stack already in mind, leave room for a stack of eight or ten, not just the two you're carrying out. For the table itself, a dinner plate around ten to eleven inches is the safe range for an ordinary table setting, anything much bigger starts eating into elbow room the second you add a side plate and a glass, and a crowded table is a miserable table no matter how good the food is.
A good set sits easily with plain linen, a wooden board, mismatched glasses, it doesn't need matching anything else to look right, which is part of why I stopped buying ornate patterns years ago, nobody notices the painted edge once there's food on it anyway. What separates a plate that lasts from one that doesn't is mostly in the body and the glaze, a dense, evenly fired clay with a glaze that's smooth under your thumb at the rim, no pinholes, no grainy patches. Cheap ones chip at the edge within a month because the glaze is thin where it matters most. Stoneware holds up to daily use better than most bone china pretends to, and it should feel steady in the hand, not light in a way that makes you nervous.
I'd put a good set of these in the kitchen first, within reach of the table, somewhere you'll actually use it on a Tuesday and not just when someone's coming over.