One thing that should go along with filming tips, are a few gripes about filming. You need to know what's good, as well as what's bad. Watching “home video” television shows has made me thoroughly glad that we didn't own a video or movie-film camera when we were young.
It's bad enough when something goes out of focus for a moment, but there's next to no point continuously shooting something that's out of focus. Apart from it being irritating, it's utterly useless. You can't see what's being filmed.
If it goes out of focus, then adjust the focus—for the appropriate part of the picture (if you're filming a person, focus on them, not the wall behind them).
If you can't manage to get things into focus, then zoom out so that focussing is less of an issue (zoom out, and stay zoomed wide-angle, and actually move in closer).
Alternatively, move a bit further back, you might be too close for the lens to get into focus (focus is an issue of distance from the object to the lens, they have a limit to the range of distances that they can work with).
Lastly, if you can't get something into focus, you may as well stop trying to film it.
The “move in close, and use wide-angle,” solution produces better results for various reasons: Focus is less critical with a wide-angle lens. Camera wobbles are less noticeable with a wide-angle lens. And the sound will be better when you're closer to what you're filming.
Turn off the auto-focus, it cannot tell what part of the picture is supposed to be in focus.
Images that move wildly around are annoying and difficult to watch, avoid it. While it seems to be a current trend in movies and television shows to do that, it's immitating bad camera work. It's a stupid trend, why would you want to immitate incompetent camerawork? Try hard to avoid wobbly shots, including shots that move around too much (whether wobbly or smoothly done), it makes people feel seasick.
Most obviously, hold the camera still. Use a support if that's difficult (whether that be a tripod, or some other handy object).
When using a tripod, use one that's designed to carry at least the weight of your camera. A camera shouldn't wobble when it's mounted on a tripod. If it does, it's broken, or the tripod isn't suited for the weight of your camera, no matter what the sales brochure might have claimed (the tripod needs to support a weight that's several times heavier than your camera—as you tilt a camera up or down, the leverage increases the apparent weight of the camera beyond the actual weight of it).
Get in closer and use wide-angle, camera movements are less noticeable that way.
Don't zoom in and out all the time, it's not needed.
Stop filming all of the time. And if you need to move your position, to get a better view, pause the recorder while you're doing so. You don't need to record everything that happens
Watching something where it's hard to hear what's going on isn't nice. It's difficult to follow what's happening, and makes it a strain.
Background noises drowning out the desired sound should be avoided. Get physically closer to what you're filming, and move away from other things that make noises.
Hold the camera steady, you'll make noises that get recorded if you make the camera rattle about, or the wind blows dangling lens caps around.
Don't fiddle with controls unless you have to. You'll record your hands scrabbling about the camera, fiddling with the lens and whatnot. And it'll be louder than what you actually intended to record, because you're right next to the microphone.
For any organised filming, use an external microphone that's physically closer to the wanted sound source, use directional microphones where appropriate, and wear headphones so you can monitor what's being recorded.
It's really quite boring to watch something that's much longer than it needs to be, and tests your patience if you wanted to learn about something you're watching. And something filmed from just a single point of view doesn't give a clear idea of what's going on.
Edit out the things that aren't needed, like the waits between one thing and the next.
Use shots that give you another point of view between some edits. Not only does it give better coverage of what you're filming, but you can use the change in view to hide the edits. Viewers, then, mightn't notice that you've edited out a few moments of something.