I think you've made the right moves to be in these discussion type sites because it shows who's in touch with reality and technology and who's not! I think past experience and certifications are all important as nicely said by my colleague, but studies show that about 80% of home buyers are searching the internet to find their homes possibly even before talking to a realtor. So I would say that someone who understands marketing esp. internet based marketing is very important, both from seller and buyer perspectives.
BUT most important of all is Pricing! You need someone who understands your local market, who understands finance and research to tell you what a particular house should be listed at to SELL, not just to list and if you're the buyer, the realtor has to understand pricing to make sure you are paying what the house is worth. The right realtor must be able to stand by his/her numbers, bottom line.
Last but not least, you have to find someone that you can work well with. Whether you are the seller or the buyer, you will be working closely with your realtor and working as a team. A successful team works together effectively to achieve the set goals.
You definately should interview 3 realtors for the job before making the decision and have your list of criteria ready. For further R.E. reading, pls check out my blog below. It has what I believe is the job of a realtor.