I recorded the meeting I had when I was getting kicked out of high school for writing an article in an underground newspaper. They didn't ask me not to, but nevertheless, I didn't share that I was recording, in case they objected. I kept it in my jacket pocket. I know what others are saying about movement noises. And everyone else was sort of muffled.
If I had it to do all over again, I'd get double-coverage. As was said, MP3 recorders are getting very small. Even digital ones that aren't MP3. And they have a much longer recording span than tapes. I picked up an Olympus digital recorder for about $60 USD that stores 3 hours, weighs 2 ounces, and is 3.75" long, 1.5" wide, and 0.75" thick. Like a tape-recorder, it has no digital communications. I'd have to "play" and "record" on the PC to transfer it. But other digital models record right to memory sticks and others have USB connections to transfer the recording, or both. But those tend to be bulkier. The advantage of those is that you can share it digitally much faster and it's in its the original recording. Even a play/record into the PC can distort the sound.
But there's still the problem of hiding it and picking up good quality sound. The taking off the jacket idea is good - wish I'd thought of it. Or hide it in your bookbag. The problem I've heard in these recordings is they're either so well hidden and muffled, you can barely make out anything, or you only hear one person well. Ideally, you'd want the recorder right in the middle of the top of the table.
Maybe you can hollow out pages in a dayplanner or a book that you can keep on the table. Get a dayplanner with a thick set of calendar pages, hollow out a section and stick your digital recorder in. At the meeting, open it to today's date with your appointment written on it so they can see it's just a calendar, but a few pages deeper is the recorder. But keep it simple so they don't admire it and take a closer look.
In addition to recording, you also can buy wireless recorders that are inconspicuous. I've seen one in a store called the "Spy Supply" that has a wireless transmitter built into a pen. Leave the other end in your car hooked up to a recorder. The great part about that is you could leave a couple of pens right out in the open and pick up the sound pretty well. The bad part about wireless is it's subject to the environment. Building structure and other interference can affect the signal. I've seen the ones with tunable frequencies drift. You could come back to your car and find out the last 3/4 of the meeting is all static. But if it does work, having the mic out in the open could get you your best quality. I think that setup is kind of expensive though. Maybe $300.
But don't use a typical cassette recorder. They make whirring noises, their recording capacity is limited to about an hour at most, and you always dread that big "CLICK" if it hits the end and stops.