Road Signals

[Eden]

Here is a good start - some guidelines put out by a local club.
Some of this may seem hard to understand if you've never done it before. I might suggest getting someone for a onetime group riding clinic for your new club. A local bike shop or somone from a local club or team might be willing to give you all a short lecture and take you for a ride to get the basics down.
http://www.cbcef.org/ridesmart_pacelines.html

In our groups we tend to use our voice and our hands - call out turns and signal them just as you would when you are alone. Point out obstacles - we usually point at obstacles (pot holes, junk in the road), wave our fingers for glass, use a sweeping motion behind our backs or a pat on the hip for thing you need to pass - like other cyclists, parked cars etc.