I would suggest interviewing several agents who list and sell in your neighborhood/ area. There are a number of questions to ask the agents, such as:
How long have you been selling real estate?
Are you a full time or part time agent?
What marketing plan do you have for selling my home?
Do you have your own website? (Look at their site, see how homes are being marketed.)
What specific plans do you have for marketing my home?
What list price do you suggest for my home? What documentation do you have to support that list price?
Some agents tell you what you want to hear when it comes to a listing price. This is known as “buying a listing.” The agent is more concerned with getting your listing than with pricing your home properly as a part of an effective marketing strategy. Overpriced listings generally sit on the market and eventually the price will have to be reduced to attract buyers. However, by that time, your listing will be "stale" and you may find it selling for less than it would have sold for had it been priced properly at the beginning of the listing.
Good communication skills are also important, so ask agents if they limit their communication with customers to a specific number of calls a week (not the best option), will they provide buyer feedback after each showing, will they respond quickly if you have concerns that are important to you regarding your listing. You want an agent that will listen to you and communicate well with you and other agents.
Generally, the best agent is the one who markets your property effectively, negotiates the most favorable price and terms possible, knows the ins and outs of home inspections/ buyer financing/ closings and can communicate effectively with you to make the process as smooth as possible.
I would suggest interviewing in person at least 3 agents before selecting the one you think best suits your needs.