Have a look at the Development Matters document in Personal Social and Emotional section to begin with and the Communication and Language will be very useful too.
Development matters
Practitioners create an enabling environment that should engage the children in play and inquisitive exploration and curiosity a practitioner should be able to engage and invite children to socialise (dependant on age of course) they can model expected behaviours and encourage participation.
Practitioner help when reading in groups, group time singing/nursery rhymes, they way adults in the room interact with each other promotes Bandura's social learning theory too.
I'm sure there are so many more points to add but I thought that might help in some way quickly if you needed something.