Several years back I had a JV Team in which all the starters were 8th graders and experienced travel ball players, but quiet ... The couple 9th graders on the team were also quiet ... It was making me nuts ... I ended up having them practice by standing in pre-game like circle with arms linked prior to and after practices and one at a time scream across the circle ... After they got the hang of it, it became their post practice and pre-game ritual ... It was an intimidating guttural tribal chant as each had their own yell ... They'd go around circle with the nine individual yells, then yelled all at once together followed by GO "TEAM NAME" ... And yes, it worked ... When they were communicating on the field, calling for balls and cheering on their team they left no doubt about it.