Starting a group
“Build it and they will come” (a quote from Kevin Costner in Field of Dreams) does not work with LinkedIn groups.
The first thing you should be asking yourself is why? Why do you want a group? Can you give it the focus it needs to make sure it is relevant, timely and appropriate. For example if your group only has 50 people in would you still want to be associated with it?
Broadly speaking there are two types of groups – open and closed. As you will probably know communications in closed groups aren’t available to non-group members so anything that is said stays within the group for the group members, whereas open group interactions can be found in public.
When the group first starts it is often the instigators which facilitate the content, generating, aggregating, curating and sharing within the group, this is quite normal. I know of some groups with 5,000+ members where the original starters still generate most of the content. As the value perception and the interest of the discussion threads grow others get involved and start to interact.
I would strongly suggest starting polls within the group to get people to interact, ensure the first few are incisive to get a reaction, and also start threads of common interest like introduction threads and similar themes.
It is the interactivity and the pin point focus with relevant audience and content that will enable the group to flourish and grow, and it is the neglect, spam and promotion of selling “stuff” within the group that will detract and bring it down.