Don't let your aerial come too close to overhead wires of any kind.
Don't run your aerial directly under, or over, or parallel with electric light or other wires.
Don't fail to make a good ground connection with the water pipe inside.
TRANSMITTING DON'TS
Don't attempt to send until you get your license.
Don't fail to live up to every rule and regulation.
Don't use an input of more than 1/2 a kilowatt if you live within 5 nautical miles of a naval station.
Don't send on more than a 200-meter wave if you have a restricted or general amateur license.
Don't use spark gap electrodes that are too small or they will get hot.
Don't use too long or too short a spark gap. The right length can be found by trying it out.