If you can't articulate this question yourself, you will have a hard time making a selection of volunteers that makes sense. You selections might tend to be random and there will be no common denominator.
People are what make phonelines work.
I am looking for folks who make contact quickly because often you don't have a lot of time to make an impression. Some people take longer to warm up. This is not to be confused with people who process things more slowly. I want someone who seems to genuinely like people. You as a person, not your skill level, make a good volunteer, particularly your ability to establish contact and empathy.