One constant question to keep asking:

What's in the frame?

Hmmm. only 3? Tough choice. How about:

- framing
- background
- lighting

The first two are rather simple to take care of, but the third can require additional equipment. So, i might suggest this alternative to lighting:

- focus/exposure

Anyway, there's my 3.5 choices.

1. Lighting
2. Sound
3. Backdrops/Backgrounds

Ligthing can be hard to achive, but good sound and backgrounds are very important!

Rogue One

1. Planning
2. Lighting
3. Sound

Good luck with your students!!!!!

TomG

1. Good audio
2. Good lighting
3. Good audio

I really push the audio part because I've had to try to fix so much of it. The bread and butter for many people with a camera is corporate and weddings (shudder). And the first thing that lets them down is the audio. In a lot of corporate stuff the inage is just there to give 'em something to watch while they LISTEN to the message. If they can't clealry hear the message it's lost. If the image is a bit crappy, well they probably know only too well what the MD looks like anyway.
Also unless the students can afford an expensive camera the damn things are designed to record the crappiest sound possible. It might be OK for kids on holiday stuff but totally useless for anything they're likely to be getting paid for.

1. Frame it well. Good audio.

2. Tell a story. If you don't have anything to say, nobody will watch, not for long. Justify EACH scene. If there is no reason for it to be there, get rid of it.

3. Know WHAT you want to shoot before you shoot it. Nothing worse then turning the camera on then turning it off 20 mintues later.

4. Avoid trying to be too cute. Too many transitions, too many effects, lots of scene changes, different fonts, all ruin final result and scream out you're a beginner.

5. Editing in itself is a art form. Take a clue from Hollywood. Many movies take almost as long in the editing room then in the shooting. Of course if that's true , you probably screwed up #1-3.

Don't use zoom unless you have a reason. Pan very slowly. Don't be in a hurry. Keep camera study. Watch out for auto focus blur on talking head shots. Pre stripe tape if possible for batch capture. Don't use too many fancy dissolves unless you have a reason for using them. If shooting music video try to get a board feed for audio. Don't shoot so much video that editing becomes a time consuming nightmare. Have fun.

I'm a beginner, basically a vacation shooter.

I've improved my editing by improving my shots = mini-tripod for almost everything, no zoom (if zoom, add 4 seconds at start, 4 seconds at end).

Now need to learn to shoot CUs in addition to long shots.

Oh, I have one more? Get Vegas ;-)

Peter

What types of videos will they be making?

The first lesson could be just to let them shoot what they want. Then you review their mistakes. This will let them know what the final output looks like and what shooting methods caused the final output, so they start thinking of "what the viewer sees" when they shoot.

I think common beginner mistakes are.
Handheld: Too jerky, even when they try to hold it still, their attention span wanders and they shoot all over the place without getting a good shot on any part of it. You don't have to film it like the final video if you can edit it later.
Tripod: Too Still, long static shots without enough angles for stimulation. They try to cover the whole event is one wide shot. Even home videos become so much more interesting if you vary your angles and use reverse shots.

Too little coverage: Another mistake is not setting each new scene or location. Wide shots can be useful transitions and will let you decide how much information to give the viewer

In film school, our first class, they showed us how to use the camera and they we had to come to the next class with a film all done in camera. No editing, no retakes, you had to have a film with a beginning, middle and end. It forces you to prepare each shot and it doesn't give you enough time to truly figure what you need to do

Composition

Headroom

Focus and exposure

(and for #3+, what everyone else has suggested, especially audio and lighting.)

When shooting, learn not to look THROUGH the camera at the subject, but look at the FRAME you are composing within.

It's like watching TV, but you have control of what's in the frame.

Gary

TorS Once past the learning equipment bit. Then I think you may know what Im going to say. But anyway as a famous Director once said Script... ScripT and Script....

SERIOUSLY

I reckon Pre planning. The Film Is done and dusted before any film is taken. If every shooting day/ Take is done. storyboarded. Then edited to a sensible logical way Then by the time shooting comes. Everything else is automatic.

I would also assign each student a different role IE Editor. sound. ect then get them to work together to blend in there different areas and work as a team.