Since I haven't seen anything about this, here are some guidelines I've gathered about being a good group leader. I should mention that this is talking entirely about informal groups. They have technically higher instance like a teacher or investor, they form rapidly everytime you are with someone, might exist for only some minutes or almost a lifetime and they are subject to constant change with people entering and leaving.

First, why is one becomes a group leader? Basically it is really easy, the one in the group who is giving the most social value will become the group leader. If you are in an existing group of people and you want to force to become the new leader, don't do it! You are only going to cause discord, the group might split and you will probably loose some friends. At worst you will be excluded from the group entirely. In an existing group, the smartest thing to do is to become best friends with the group leader and keep giving value to everyone. Usually it is enough to be of the highest value males anyway, you don't need to lead at any cost. Eventually over time you can take the leading role naturally. If you want to form a new group and be it's leader you can do this by setting up events, inviting, starting study groups and so on. It is fairly easy since most people are somewhat afraid of being in charge and the work that comes from it. Notice: If you find yourself in a leading role there is always reason for it and you should not shy away from it. Once I had build a group and didn't want to take the responsibility, so I literally said "I don't want to be the leader" I regretted that later on since the quality in the groups activities dropped drastically.

Next, If you have reached the status of being a group leader, how do you maintain that position? Obviously you are going to be responsible for everything good and bad that happens to that group and you have to consider the capabilities of it's members. On the other hand you want to put in as less effort as possible and want to take as less responsibility for bad things as you can. To reach that

1. You only say that you are sure of something when you really are sure of something. It builds a stronger leading role if you are extremely sure of what you are doing but if something goes wrong the group will hate you for leading them on and you don't want that. This is not about not telling an Idea that you have, this is about making sure that everyone is on the same page. don't tell "I'm 100% sure where it is" when you only vaguely remember a direction.
2. In conjunction to 1 it is a good idea to start with activities that you really can be sure of since it will build trust in you as a leader and future failures will be forgiven much easier. At the same time, don't forget that more interesting activities give more value.
3. Be creative. Sometimes being lost is much funnier when you call it a night walk.
4. Stay calm. You are in charge.
5. Get other peoples opinions. It is really good to feel in what they are willing to do and get their additional knowledge.
6. And this is very important, hand off tasks to other people. When you have no Idea, why not give your approval to the one that obviously has an idea? Also this can easily kill someone trying to overthrow your position, by giving him a chance you will give value to him and if he fails he will have to step back and if he succeeds it will strengthen your position as being a good at delegating. This will work best if you don't acknowledge him in any way as a threat. Since otherwise he might be able to turn it around as a win against you.

If you want a really good example for leading, look at Captain Picard in Enterprise:TNG. Also I like watching wildlife documentations on animals living in packs, the rules there apply pretty well to humans too.

When you are doing it right, in a well established group, you sometimes can lead by just saying 'yes' or 'no' to the proposals of the members of your group.

What I've had a problem with for a long time is when things went wrong. I let myself get hit by it and the critique for it, much to hard. Thankfully there are many times members of the group that are willing to help you out of it since they gain from your leadership. (the leisure of not needing to lead, stability in the group, their status)

I hope this helps you guys a little.