First of all, there's a huge difference between being the leader of the characters' party and being the leader of the players. In your question and in your answer, it seems that you've mixed them. As such is the case, I will try to address both subjects in my answer, but I'll be far happier to know on which one I shall focus.
For this answer, table level means the level of the players around the table, where the players tell the story. Story level is the level of the actions and characters inside the story. If we take a fight against a dragon as an example, the dragon is in the story level fighting the PCs, while the players and the GM describing actions and rolling the dice is the table level.
Leader of the characters
I believe that this is the easier thing to handle, as everything that happens in this level can stay in this level. This means that in the table level, everyone can participate, but in the story level there is a person who leads. This is a huge difference. As such is the case, I believe that the key here is to let the players talk between themselves and after they've decided about their route of action they should present it as the leader's idea or something.
Another idea might be a weak leadership, with the leader having the final vote, in cases of ties. This, again, lets the leadership be entirely in the story level, and thus it won't interfere that much with the players themselves.
Leader of the players
This is the more difficult part, but again it can be solved. Being the leader of the players means that one is the PM of the players; she is the one who will decide about the courses of action.
For this level, I think that the first thing to do is to talk with the other players and see if everyone wants it but also to decide upon the rules and habits that the leader should follow. This ensures that everyone is on equal grounds, and that the leader won't disuse his or her power. Personally, I prefer the extra vote kind of rule, meaning that the leader has an extra vote in times of ties between the players ("2 wanna go south, 2 wanna go west, so the leader is the decider").
In addition to that, though, the leader should try as much as she can to make sure that everyone is having fun. If someone is bored, it is her duty to make sure that this bored player will participate. In a nutshell, the leader should act as a lesser GM in this particular matter.
I believe that this deserves a section of its own. As I see it, rebellions in the party, be they in the story level or in the table level, should be discussed beforehand. Rebellions can be seen as a revenge act, or as a way of saying that one doesn't like the leader or something, and this can lead to much hard feelings between the players if it goes out of hand. Due to this reason, I truly believe that they should be discussed beforehand.
A few things to keep in mind that just didn't fit anywhere else:
Firstly, one should keep in mind that the leaders in the table level and the story level don't have to be the same one. If Bob wants his character to lead the players' characters and Lisa wants to lead the players, they don't have to be the same.
Secondly, there doesn't have to be a leader in the table level in order to have one in the story level, and vice versa. They usually coexist but it is not mandatory. Bob's character can lead the PCs without the need for Lisa to lead the players or vice versa.
Lastly, the players can and should switch leaders if they don't enjoy the leadership of a certain player and the characters can switch their leader too should the PCs' leader prove not good enough or the like.