Some important items I'd ask about. My .02c:
1. Communication - if the agent is lousy at communicating with you, move on.
2. Experience - how long has the agent been in real estate, and is this their full-time job or only a part-time commitment? This is significant because it makes a difference if/when things go sideways during a transaction. A good agent has made the mistakes (and hopefully learned from them) that can't be replicated except through experience.
3. Marketing exposure - getting the photos/tours/websites is vital, but getting them promoted out to the widest area possible is essential. To make a fishing analogy: you may have the greatest bait in the world, but if you're only fishing in a tiny puddle, you're unlikely to catch the big fish that you're looking for. An agent needs to be able to put the property out everywhere for you, which is one of the advantages of the global brands. Smaller brokerages can't compete with the $$$ that the big spend to increase that exposure.
4. Network - is the agent well-connected with the other local RE pros? Some agents people will go out of their way to work with, while just the opposite is the case for others. Also important is the rest of the support that the agent can offer: painting, cleaning, staging, gardening, plumbing, inspections, etc. can make the job much easier for you if they already have a list of vetted pros for you, if needed.
5. Availability - does the agent have time for you? If they're carrying 20+ listings, you will not get one-on-one attention, and details may get missed/dropped.
5. Cost - is always important.
6. Escape clause - if you're unhappy with the service, you should be able to cancel your contract with the agent. Everyone is all promises up front, but if they're not delivering, and you can't get them to effect some change, you should be able to go separate ways.
I have many more, but these are some of my top suggestions. Hope this helps.
-IR2