Some tips from my life:

Try and get everyone to have the same goal. This helps everything else, and gives a reason for the group to get together.

Try and find people's strengths and motivations. Some people will do more work in a certain area than they would in another. Some people will hate doing one part but love a different one. Playing to other people's strengths helps everyone do a better job, as well as making individuals feel more responsible.

Sometimes people just don't know how to start. If you give them tangible guidelines then it takes a lot of the cognitive load off of them. On the other hand, it eats more of your attention that might need to be spent elsewhere.

Hope that helps.