Captains are leaders on the ice, in every way.
A captain has a great attitude and is the kind of player everyone wants to skate with: fun, upbeat, plays hard without being chippy.
We need captains who are unilaterally committed to parity--for all other skaters, friends and teammates as well as strangers.
A captain should be in the upper half of skill level at the session--we want the captain to be able to look at other skaters for parity reasons, not be distracted by trying to keep up with the game pace.
Most captains became one after being recommended by other captains, who know who the leaders are and what the position's responsibilities are; the current captains are a good judge of what we need.
Some people hear that captains play free. While true, it's only a small compensation for all the work captains do. People who are interested in being a captain because they will then skate for free, don't have the motivating factors or personal skill set we're looking for.