Universal Hand Signals
Whether riding in a group or riding alone, hand signals are critically important to your overall safety. Motorcycle safety using hand signaling lets the other people (mostly automobiles) around you know what you are doing. Turn and brake lights are small, and often not familiar to automobile drivers. Hand signals greatly increase your visibility and over all safety. Hand signals are really important when riding in groups, because of the limited visibility of the riders behind you, but equally important when sharing the highways with cell-phone talking, or equally distracted drivers that likely don't even know that you are on the same road with them.
In motorcycling, hand signals are extremely important, not only when riding in groups of motorcycles, but also when riding in traffic with cars. It is always a good idea to give the automobile driver a little more visibility about your intensions.
When riding in a group, the person behind you likely does not know what's going on ahead of you. The courteous rider will relay signals back through the pack.
Start Engines
Left Turn
Right Turn
Hazard Left 
Hazard Right
Speed Up
Slow Down
Single File
Staggered Formation
Tighten Up
