Managers, how do you go about choosing an insurance broker?

My employees (and I) have been very unhappy with the advice and service that our insurance broker has been providing us, and it’s time to make a change. He was in place when I was hired by the company, and I’ve never gone through this process before. Any advice on making a good decision? What sort of questions should I ask? What should I look out for? Is there some sort of accreditation that I check for?