Yes, most ppl miss the fact that this is a family oriented forum and rules of decorum do apply, unlike places like reddit, which are totally unregulated. It's honestly no big deal, it happens, just please don't let it happen again 😀
Wow, where to start. Platform. MITX, mATX, atx are most common, especially if you don't like 'big' but even some ATX mid towers get pretty huge, my Define R5 and CM 690 II Advanced are almost as big as a full tower.
Looks. 2nd most important decision, you have to look at it, deal with it, live with it. So where do your tastes run. Me, I'm a classic, much prefer my pc to look like a pc, not some cheapo Manga explosion called a gaming case, like what Xpevia and others produce. So my R5 was perfect.
Details. Apart from general looks, what else is important. Front facing usb, top mount usb, optical, temper glass, leds capability, fan controls doors, psu shrouds, etc. All the little things. My R5 sits on the floor, so top mount usb/audio is a serious bonus as I no longer have plugs and wires sticking straight out. If the pc is desktop, front or side USB would be far easier than top, especially on a tall case. It's always the little things that aggravate the tiss out of you right after the new case smell wears out.
Quality. It's so important that it is least important at the same time. Many better cases are all approximately the same, good. For most ppl, after the initial build, they'll not touch hardware other than for cleaning, so build doesn't take any precedence. So you can ostensibly get away with a cheaper case, as long as it does the job. That's where the more expensive cases excell, in the options. Like better wiring capacity, easier mounts, grommets on pass through, thicker glsss/acrylic, stronger frame and panels etc. A perfect looking case, that bends if you breathe on it, really is next to useless.
First, make a list of what's important to you, must haves, be nice to haves and bonuses you wouldn't mind.
Visit pcpartpicker.com. Open up cases, and near the top right is List / Detailed List. Click on list. This'll bring up pictures of the cases. Find some that look right, maybe 10-12. Then start Google ing reviews, the more professional, the better. Compare results to your list. Put into 3 piles. Keeper, maybe, toss. Narrow down your keeper/maybe lists to 2-3 each. You'll end up with 2 cases, 1 keeper, 1 maybe. Then apply budget and weigh in.
End result = case you should buy.