A team leader must be a good and strong communicator. He or she most be committed to projects and be able to get others passionate and enthusiastic about projects.
A team leader must be responsible, positive about task, respectful, fair and kind, be an example of intergrity, organizing and understanding.
A team leader should set the tone, and therefore not be afraid to speak out, set boundaries, aims and targets for the team. But there are good ways of doing this: not aggression, but being a good role model, practising what you preach. Reward those who do well, and those who try hard even if not very successful. Foster togetherness and forge friendships, never encourage divisiveness.