First things first. In my opinion a good group requires the joined forces. The more the merrier is often true. But it then also means that one has to be ready to compromise. If you wish to administrate a group alone, then you may not reach the success. And that is because the group can not grow beyond certain limits. Groups administrated alone are in danger to turn into a dumping grounds. People may continue contributing in them, but they really never visit the group pages to see what other group members are doing.

So, be ready to collaborate. Form a band of at least three people, who all get to administrate the group. The third person's role then is useful to avoid ties when opinions disagree. And three persons is often good to make sure that there is at least one available, if some of the group members has something to ask from admins.

Then makes sure that one of the team members is technically skilled, and one is good with languages. So, the nerd knows how to set up the group in multiple languages, and the language genius is able to make sure that the group becomes internationally appealing. The third could then be socially skilled. I've seen and left few groups that turned out battle grounds, when admins where not able to work together. So, someone working as a mediator can turn out as useful.

And only after all this becomes the choice of topic. Having more administrators then also help to choose the topic. It should not be too specific. If the topic is very narrow, then there will never be enough members to join and contribute. And if the topic is too broad, the group may turn out unattractive. People does not become and stay inspired if there are no challenge to participate. And again, the danger to become a dumping ground only increases.

It does not mean the group would need some weekly or monthly challenges declared. But the well chosen group topic, and contributions seen there, can work as a motivation for others to join the group, contribute, and even visit the group pages regularly to see what other members are doing.