Meetings (in my experience, and for me right now, at least) tend to be about four things.
Solving problems (or perhaps 'making decisions')
Generating ideas
Discovery (i.e. figuring out the shape of a thing -- maybe what your problems are, without trying to solve them yet)
Transferring information
Some of these can be accomplished by means other than a meeting, but often meetings are the best way of doing the thing in question (for the immediate local version of the thing -- all of the above are sometimes better as meetings, and sometimes better other ways). Even transferring information, the poster child for 'this could have been an email', is sometimes genuinely best as a meeting (though I think that requires specific intention about why it's better that way).
Each of these demands slightly different approaches from meeting participants. Obviously, an all-hands is very different from a writers' room, but even two meetings consisting of the same three people should function very differently if they're seeking to transfer information or solve problems.
I think bad meetings, really, come when we conflate these functions. Or worse, don't think about them at all. Fundamentally, if you're setting up a meeting to generate ideas, you want to design it differently than if your goal is to solve problems. Likewise, for me as a participant, I need to be in different headspaces, and do different prep, for each of these things.
Basic example: for problem solving, I might want to bring a strategic frame of mind. It's useful to be able to weigh an approach and find issues with it, be critical, look for tradeoffs. If you bring that same critical lens to idea generation, it can be stifling and counterproductive.
(I do think there is some flex in this -- you can have meetings that mix categories that still work well. But I think that flexibility scales inversely with the number of participants. Three of you can probably manage a meeting that does three of these functions. Six should really just stick to one.)
Here's some ways I think about preparing for meetings of different functions:
Problem Solving: What are our guiding principles for making these decisions? Who are the stakeholders? What criteria are we trying to satisfy? (And then logistical stuff like 'who is responsible for capturing the outcomes and following up on next actions?')
Discovery: What questions should I be asking? What does success look like? What isn't in this picture -- what are we missing? Could I explain this clearly to someone else? What information am I missing to be able to do that?
Information Transfer: If I'm giving out information -- making sure I have my material organised and know what I'm actually trying to communicate. If I'm receiving information -- come prepared to take notes so I can engage with the material.
(If there's nothing at the level of note-taking, then, yes, maybe this could have been an email. But even then -- sometimes there are emotional management components at work as well -- telling people something to their face, and giving them the opportunity to ask questions. Even if 100% of the output is captured in writing anyway and no one actually does want to ask any follow-up questions, the decision to do things that way is sometimes important.)
Idea Generation: I try to prime myself ahead of time, as I would for solo idea generation. Reading some related and random stuff. Looking for sources of creative entropy. Warming up with some exercises. Making sure I have scrap paper at hand to scribble during the thing itself.