1. Work out what's expected of you
Schedule regular reviews with your boss, if you have one, and get as much feedback as possible. Defined expectations also provide clear criteria for self-assessment.
2. Ask each team member what they, as individuals, want from you as their manager
Take every chance to learn about them as individuals, and to gauge opinions and the general atmosphere: you are managing people as well as their work. Above all, listen more than talk: your ears will teach you more – especially about your own impact - than your mouth.
3. Make sure you delegate the right tasks to the right people