A thorough preflight will prevent more launch accidents and flight crashes than any other thing you can do. Start with an airframe integrity bench check before you leave for the field. Check for and repair cracks in the wing, the fuselage, and the empennage. Too many crashes are caused by loss of electrical power in flight. Look for meter readings consistent with those of new packs.
Lower voltage can indicate a dead cell in the pack.
At my home field two. Airplanes were crashed on launch in two weeks because of elevator control reversal. Using a four-channel radio, one pilot switched airplanes and neglected to reverse the elevator servo. Another pilot performed about a half-hour of programming in an advanced computer radio, and proceeded to launch with the elevator reversed. It's believed that the fault was caused by incorrectly copying the program from one model to another.