Besides Ted's:
Tips for actually keeping the camera on the rocket:
Zoom out unless you are experienced. I see lots of people zoomed way to far in and the rocket never makes it in the frame.
USE THE VIEW FINDER this makes a HUGE difference in the quality of the footage
Know the speed of the rocket. (does the rocket look small and have a big motor?) Have a mental video of what the flight might look like before the rocket launches.
Be smooth: Use one slow, arching motion to follow the rocket, lots of people jerk the camera around to much, trying to center it on the rocket.
It's not good to film a rocket with a tripod, I find you need more control over the camera.
It's also interesting to have different angles. Personally, I like the 3 cam set up: Pad cam, onboard and ground cam that tracks the rocket.
Editing:
Unless it's a rather unusual rocket, don't include pad set up. It might be important to YOU but no one wants to see more then like 10 seconds of pad set up. I find myself skimming over the pad set up completely.
If you use music, don't include it for the boosting stage in the flight, If the music overpowers the sound of the motor, it ruins the effect (IMHO). Save the music for the recovery.
I like to use a picture of the rocket instead of a pad set up.
Clearly label what motor is used.
Slow motions are cool but they shouldn't last forever. Try to shorten slow motion time to only the interesting parts of the flight.
Typically, My ideal video for one flight is from 30sec-1:30sec.
All of this being said, I break my own rules quite a lot.
Check out my youtube channel in my sig for my videos.
All of these are my own personal tips accumulated from a few years of filming club launches.
Alex