The whole purpose of hiring a real estate agent is to buy or sell a house more efficiently than you can do on your own. With that in mind here's something you want to keep in mind.

When interviewing real estate agents make sure that they have access to the local Multiple Listing Service (MLS). The MLS is a database containing most residential real estate on the market in a community at any given time. If you're selling a house you will have much more exposure if your house is listed in the MLS. If you are buying a house you will be able to learn about more properties that meet your requirements.

Most real estate agents have access to the MLS. Just make sure that the one you select for your agent has this access.