The reason that an agent works the way they do to represent you, in addition to regularly working in the local market, is because they have an intimate familiarity with the activity in that area.
Remember, especially in the real estate business, some things can't be explained as simply "black" or "white," but rather, fall into the category of "gray." These are the circumstances that can't be explained by an internet search, a flyer, or a book about real estate.
It is also worth noting that hardly no two deals are the same, so new scenarios are always taking place. An active agent in will be familiar with new possible problems and anticipate them before they happen.
If you are planning on selling a place in Aberdeen, MD, hire an agent that is involved in and around Aberdeen, MD. If you are buying or selling a home in Bel Air, MD, hire an experienced agent that works in Aberdeen, MD, Havre de Grace, MD, Bel Air, MD, or just generally throughout the Harford County area. A good rule of thumb is that if the agent's office is more than 30-45 minutes away, he is probably too far to adequately represent you and your interests.
Get references. If the agent has satisfied customers in the past, ask them to give you the names of some of the those people. This will support their representation that they are experts, and thereby, give you the confidence you need to let them do their job.