Here are my two cents.
First, should you use one and when?
Your super novice lifter certainly doesn't need to be wearing one yet. They should be focusing on body control and movement perception, technique, and the like. You're probably not going to be wearing one when you do push ups, moving the couch over there, or riding a bike up hill, so if you have only begun start by letting your body figure out how to coordinate itself to handle weight.
If you compete, and you're pushing your limits, get a damn belt. It doesn't make you weaker, it allows you to actually get tighter by having something for your "core" to brace against. If you're scooting that couch over there, wouldn't you rather push your foot against a corner between the floor and wall rather than just against the floor?
What belts for what?
I have three belts, I use each for a different lift or movement type.
How to wear and use a belt
I've read that you shouldn't cinch it, and there should be enough room for you to put and hand between yourself and the belt. I don't know if I agree with this. I don't want to distend my stomach anymore than I have to in order to brace against the belt. On the other hand, I don't think you should go corset tight, where you've got two assistants helping you get it as tight as possible. I just tighten as far as I can with my own two hands, no leaning against a rack, and it's done.
This next trick is key: push that sucker down on your belly. This isn't a fashion belt for your sweater dress, this WILL give you a muffin top and an enhanced FUPA, and that's okay. My coach Jesse taught me to push the belt down and breath out against it across my lower abdomen. What a different that makes!
This is one reason I can't use the cloth belts for anything other than the bench, they slide right back up. The leather ones stay in place much better.
Breath out against the belt? What does that mean? It means you take a big belly breath that fills your stomach and push that against your belt. This is anaerobic territory, so the fact that you'll be chest breathing to keep the belt in place doesn't matter all that much.
When to use a belt?
I've heard a lot of things thrown out there. When your technique falters. Around 80%. Etc. I like to wait until I feel like I need it to be tight under a weight. You know that feeling, where you take a weight out of the rack and even if your back is straight, you can feel your core struggling. Ideally, as your PRs increase, the point where you need to put on the belt increases, too. On squats, I try to only put it on once I've reached my working weight as suddenly that weight feels 20 lbs lighter since I'm not constantly trying to steady myself under it.
I also never use a belt for snatching. No reason other than I just couldn't get used to the feeling. Maybe my snatches are still to light (duh, weakling).
Belt up and lift heavy shit! It makes you a more useful human being.