What type of team head? Here's a little write up on student heads.
384 has had a few different setups for student team leads/project managers/presidents.
1.) Hand vote. Simple, yet easily swayed. I'm not a huge fan of this since it's popularity that matters. Ironically enough, this is how I was elected.
2.) Private vote. Simple again, place name for prez (and other officers) on a piece of paper (usually has the names on them for those in the running, mostly seniors, and they just circle them then). The votes are counted and their is a winner.
3.) Mentor meeting. Most undemocratic and most comprehensive. This vote is a majority done by our mentors on our team, including all parent mentors. This was about 12 people. Anyway, the merrits of all contendors was discussed and what they could offer. My favorite since it puts the best man in the position, not the most popular.
As for what our team head does, well, that's varried on the person and the team. I've seen people do nothing, people do everthing (including building and administrative), and people in the middle. I find those who are away from building the robot and other parts do the best, followed by those who build, then those who do nothing.
They are important to have not only because it's eaiser on the main team head, but because it unifies the student part of the team.