Mary,
Your best bet is from either a referral or to interview your prospective agents. You are correct "slick" sales pitches do not help. You will need to ask about their experience and their track record. How many homes they have listed for sale now and what their marketing plan for your home would be. How long is their average days on market? Where are they going to market/advertise your home. In other words to be blunt how are they going to sell your home? Now most large companies have scripts and practiced sales pitches. Just get them off the script and see how they act. I will admit I use to have a "listing presentation". I have not used it in over two years. You really need to "interview" any agent just like you are hiring for someone for a job. After all this is a job where we work for you. Our job is to get you the most money for your home.
If you do need a referral to a top agent in your area feel free to contact me either through my profile on Trulia or one of my websites listed below.
Hope this helps, - A few hours ago