Please don't crowd the head!
In triples, only the two vices should be standing behind the head. The leads should be at the back of the green.
When skip A is on the mat, then the vice for team A should be in the head to communicate with the skip. Once the skip's bowl comes to rest, skip B takes over the mat and vice B takes over the head.
Only one vice should actually be in the head at any given time until the end is completed. Then both will agree the score - after measuring if necessary. Normally the team conceding the end would do the measuring. In a pairs game the same rules apply only it is the leads alternating in the head.
A bit of etiquette: Please remember that to play well you need to concentrate. By all means be sociable on the green, but don't talk continuously and distract other bowlers. Cell phones are also a distraction. Please keep them off the green and preferably turned off while you are playing.
More information here.