I had just answered a similar question for another person when I came across this question. Here is the gist of that answer:
Always interview several agents. Find a good personality fit. Rely on your instincts. Be careful if you get a bad feeling about someone.
Ask a lot of questions. Write the questions down so you don't forget an important one. Include a range of subjects, including some about the local market, how the agent handles particular situations, the home buying process and the agent him/herself.
Eliminate agents who blow off hard questions, offer terse answers, provide answers that sound off, or act as if you should not bother yourself about understanding the process.
However, it is perfectly reasonable for an agent to research an answer and get back to you. If the agent does get back to you quickly, that is a good sign.
Good communication is among the most important attributes you should consider when hiring an agent. Lack of communication skills is among the biggest complaints from clients who have had a bad experience with an agent.
Thus, paying attention to agents' communication skills before hiring him or her will go far toward making sure you have a good experience with your next home purchase.
Prudential Real Estate of the Rockies