Inadequate attention paid to experimental uncertainty. Poorly executed graphs. Inane, absurd, or insupportable statements. Failure to come to grips with results. Improper or awkward grammar that fails to measure up to the Freshman Studies standards.
Electrical instruments are vulnerable to damage.
Never, for example, connect a voltmeter across an unknown potential unless the meter's full scale setting is known to be greater than the maximum posible value of the potential difference. Always make good electrical connections, which means solder connections whenever possible. Use shielded cables. Rarely if ever use clip leads, and never remove the leads from a vom or digital multimeter. Always unplug soldering pencils before leaving the laboratory.