Look for earlier threads and do a search on the subject on the web.
#1 Do not attempt with an all-rookie group
#2 Do not do formation take-offs and landings until you have a great number of hours. After that, make sure TO and Land are coordinated in group, with the airport manager (who may not approved) and with tower (who may not approve).
#3 Only one airplane in a formation flight squawks an assigned beacon code. All others have transponders in standby until the formation breaks. Lead aircraft has beacon code and communicates with ATC as in: "Approach, Cessna 345 is a C-172 formation flight of 3 over xxxx request flight following on our route to yyyyy, maintaining 3000 feet." When given a code, only the lead squawks and communicates. ATC expects to see a single beacon reply and two primary targets in close proximity.
#4 Know who is leader and who is wing in all cases.
#5 Communicate with each other on Multi-com (122.75) but keep conversations short and precise. Multi-com is not a CB.
#6 Discuss on the ground in detail before the flight, where you will formate (e.g. the "y" in the interstates and we will depart to the Northeast), who is lead and how you would change lead if this is to occur, comfort distances for each member, formations to be flown, and how you will break ranks out each formation. The last one is important in case someone has a problem - know how each plane will "break" into clear air.
And finally, as most who have formated will tell you - you will close on an airplane ever closer and closer until you feel for yourself what a wingtip vortice or prop wash (even off a small plane) will do to you and then you may just scare the xxxxx out of yourself. Be very careful when bringing two pieces of aluminum close together.
Job Descriptions:
Leader - Lead aircraft - calls formation types to be flown, keeps aircraft extremely stable so that other aircraft can formate on him/her, watches for traffic and terrain, calls turns and breaks.
Wing - one or multiple aircraft. Formates in direction as directed by leader. Watches wing and aileron of leader or next wing and follows directions without question.