Having intimate knowledge of the local market place is one of the factors that makes an agent superb. No matter how good an agent might be, it's impossible to cover an enormous territory successfully. If you're buying or selling outside of your agent's domain, ask your agent to recommend a local agent who can better serve your needs. There are many qualities that define a great real estate agent. One of the most important is trustworthiness.
Experience also ranks high on the list.
However, a relatively new agent can do an excellent job for you if he or she has adequate support from experienced colleagues. But, there's no substitute for high ethical standards. If you don't have personal experience with an agent you're considering using, be sure to check references. Ask each agent to give you a list of recent clients he or she has worked with. Give the references a call and ask them if they would work with the agent again.