A radiogram’s number is the first thing we send. If a receiving station has indicated, “ready to copy,” the next word out of our mouths should be “number.” Not “please copy,” not “message follows,” just “number.” It’s what experienced traffic handlers expect to hear. 
Next, we say the number itself, one digit at a time. So, if the message number is 12, say “number one two,” not “number twelve.” If the number is 131, we say “number one three one,” not “number one thirty-one” and not “number one hundred and thirty-one.” Finally, we say “zero,” not “oh” in numbers like 101.
(This is the second in a series of short traffic-handling columns I submitted to the Kosciusko County ARES newsletter.)