When you do rocket launches for an audience you always want to test fly the rockets before hand to work out any of the little problems that might arrise. I didn't do this for my first few rockets since I was trying to demonstrate the method to a few people. As it turns out, my professor and his family came out to watch the maiden voyage of the three-stage rocket.
At the beginning things looked great, the rocket engines all fired at the right time and the stages ejected at the right time. Unfortunately, the parachute didn't open. This rocket was approximately 900m up when it turned over and became a javelin. After pulling the buried six inches out of the ground and doing some repairs I decided to launch the rocket again. This time, the stages decided not to eject so they all got burned to ash. Oh well, one rocket down.
As a replacement for the three-stager I bought a smaller two-stage rocket. It worked great until I launched it at Correlieu Secondary School in Quesnel, B. C.. The wind caught it as it came down and it landed on the road just as a car came around the corner. Two rockets down.
A bane to all rocketeers is the high altitude winds that cause the rockets to come down outside of your landing area. Rockets 3 and 4 were lost to trees and wind in Vancouver.
The pride and joy of my rocket collection is the Space Shuttle since it acts just like the real shuttle does. When the parachute in the gas tanks ejects, the orbiter disengages from the tanks and glides down to earth. This rocket has crashed every time, but one, that I have launched it. Still works though.
So remember, you can plan all you want and take all the precautions you want but if Murphy is around he'll have his way.