I went througth the exact experience. You'll need to a couple of things:
1. Ask friends you have back home for referrals. Develop list of concerns that you have and ask each Realtor you interview the same questions, then you can compare their answers.
2. I like the idea of asking some of your new friends of they know of a Realtor in your new home town. Sit down and go over your situation, and see what they say. They can probably find you a Realtor that can help.
3. Look in Trulia Voices for a Realtor that works in that area. Ask the same questions
I would recommend calling a local agent that you may know or have worked with and ask them to refer you to a Realtor in the location that you are trying to sell. Many Realtors have excellent contacts throughout the US and abroad and know of the agent's areas of expertise, etc. Good luck!
The question is: How do you find a good one? A couple of suggestions. Search online for homes in the same neighborhood or zip code as the one you want to sell. Make notes on who the listing agents are. Look for a pattern; very often, a few agents will be dominant in a particular area. That's one place to begin, and really the one I'd recommend.
Another option is to contact an agent where you are now (preferably someone you know, someone you trust and like) and ask for a referral to an agent in the area where your home's located. Most firms have referral programs. That means a couple of things: First, the agent you contact probably will receive a share of the commission, so you might as well ask someone you know, trust, like. However, it also means that you'll probably have a better shot at getting a good agent than if you simply opened up the phone book, called an office, and got whoever was on desk duty.
After you've identified 3 or so possible agents, then you'll want to interview them, as Loni suggests. And there are plenty of threads on Trulia about how to choose a listing agent.
Hope that helps.