I have not worked myself as a call handler but I wold imagine they need to be clear, concise and articulate. Fast at typing on a computer also.
Honesty, good communication skills, speak clearly, and be cheerful!
Most important tip will be to respond to calls that come in. be sensitive to all calls that come in. Listen carefully to what the person on the other side of the call is saying, especially if they are axioms or scared. Be understanding toward the other party feelings and follow the polices and protocols in place.
Communicate and confidence