Podmog: Any particular areas? I'm looking forward to reading other contributions here. Here's a first salvo from me:
I've been involved in toddlers for over 6 years, and different groups. One thing that seems to work well IME, is to have an 'everybody tidy up session' towards the end, followed by songtime in a circle. This way everyone does stay to the end if they possibly can, and everyone helps tidy up.
Try and have someone responsible for welcoming and getting to know newcomers. Also encourage everyone to get involved; explain about your routines - tidying up, drinks, etc., and tell them ways they can help - joining the 'setting up' rota, or washing up the paintpots, or whatever it is, so that the tasks are evenly shared.
If you can, rope in extra help to serve drinks, and healthy snacks for the children.
If possible, designate a "baby space" where small babies have some sort of protection from larger toddlers.
If you have the space for larger toys, and ride-on things, make sure again that these have a designated space, and probably a limited time too.