1. Each captain is different
The first thing to remember is that there is no one set of characteristics possessed by effective captains. Very different personalities can be successful captains.

2. Mentally strong
The mental part of the job is arguably the hardest part. All captains should be mentally strong. Inevitably, the captain will be criticised at some point, both within and outside the team.

Equally, the captain needs to remain focussed and aware whilst under intense pressure during a game, so that he can make the correct decisions at the right time. To cope with this requires considerable mental fortitude.
Some captains say that the mental aspect of captaincy is the hardest part, because there is so much more to think about, as well as playing.

3. Excellent communicator
KISS – Keep It Simple Stupid
This is a skill required by all captains. The captain will need to encourage and manage on-field communication between all the players, as well as maintaining effective communication both with players and between players and the coaching staff off of it.
However, this does not mean that the only voice to be heard on the field should be that of the captain’s. Indeed, the captain should only speak when necessary, being able to keep his communication concise and to the point.

4. Emotionally disciplined
“Fire in the belly but ice in the brain.”
This is important for three main reasons:
a) As a role model the example set by the captain must meet every expectation he has of the players. For example, if the captain becomes angry with the referee and constantly questions his decisions, then he cannot expect his players to accept refereeing decisions themselves.
b) If the captain loses self-control and vents his anger or frustration (whether against an opponent, teammate or the referee), he will have lost the ability to make rational decisions. His own performance will also suffer; a loss of emotional control will affect timing, co-ordination and the ability to “read” the game as awareness becomes more narrowly focused.
c) A loss of emotional control will be seen as a sign of weakness by the opposition, boosting their confidence whilst undermining that of the team. This does not mean that your captain becomes an emotionless robot, devoid of passion.

5. Knows the players
The first thing you have to remember as captain is while football is very much a team game you are dealing with individuals who are all different in attitudes, temperament and experience. Thus you have to find out each person’s strengths and weaknesses… And you have to find out which players best respond to the carrot and which to the stick.
The captain should have the ability to deal with each player as an individual. Consequently, he will know what motivates different players and how they prefer to prepare themselves mentally for a game (not all players respond to being shouted and/or sworn at!).
He or she should observe players both on and off the field in order to learn how best to deal with them.
The captain needs to know which players are best left alone, which require a quiet reminder of expectations and which need a more forceful articulation of what is required.
The captain that also takes time to get to know his teammates as people and not just players will ultimately achieve far more respect and effort from them.

6. Self-confident
“Don’t ask me how I played. I always think I played well.” A self-confident captain inspires confidence in others. It also helps him maintain his own performance.
This is easy when things are going well, it is harder, but arguably even more important, to do so when the going gets tough. The captain needs to make sure he at least gives the impression of confidence in these circumstances.
Looking and acting confident will, sooner or later, lead to being confident.

I always look for a captain thats been at the club for a while and has the club as one of his favoured clubs. High mental attributes in influence and determination and a personality such as level headed, determined or loyal.

Hope this helps!