Most people are uncomfortable about receiving honest, constructive feedback. Managers can be resistant to requesting feedback and team members can be resistant to giving it due to possible ramifications.
Good or bad, feedback is a critical aspect of personal and professional improvement. Without the views from others, bias can get in the way of objective criticism or even positive reinforcement. Ultimately, managers and their team members alike will have a stunted perspective which hurts job performance.
The easiest thing to do is just ask. For a manager, you can request feedback from colleagues via paper, spoken word or electronic mediums. Asking questions that ask what you should start doing, what you should stop doing and what should continue are good broad topics to start with. In general, it is important to not only ask people you like, but those who you respect. The key thing is getting objective feedback that won't warp your sense of importance.