There are some photography books in the library, can't remember specifically, that will tell you some of these things. Look for those focussing on portraits and wedding photography, they will give you some idea.
Basheer at Bras Brasah (topmost floor), a graphics book store, also carry a book on wedding photography that I had borrowed from the library and found it very useful.
The basic idea is to let everyone look as natural as possible, the most difficult being the placement of the hand.
If you can make the auidence felt at ease and natural with themselves, then you are already a pro!!! :devil: And if every Tom, Dick and Harry can do that, then we, professional wedding photographer will be out of job! haha..
Jokes aside, seriously, all wedding photographers have their own tricks up their sleeves. One way to lighten up everyone is to crack jokes with the auidence. When everyone is laughing, chances are, they are at ease. One trick which I always use, is to have someone from the auidence shout "on the count of 3, everyone say cheese"... Definitely need to identify a few jovial people in the group to help out. That way, everyone will not look so tense in photos.