The first thing to think about when looking for a realtor is: do you need a realtor?
If you are totally new, then in the short run a great realtor will be less expensive than a real estate seminar. However, a bad or just average realtor will end up costing you a lot of money.
If you are experienced, a realtor can sometimes be helpful but is not a necessity. My general rule of thumb is: if it is listed, I bring in a realtor. If it is listed, a commission is being paid. Why not give someone a piece of that commission for representing your interest? Also, a realtor can be helpful if you are investing in an area that you are not familiar with (not a recommended strategy, by the way).
One place I like to look for realtors in an area is at real estate investment clubs. The realtors that attend those understand real estate investing. Also you can get referrals from other investors. The last thing you need is a realtor who only knows how to fill out the standard form.
Another place is to look through the free real estate magazines that are often available at stores. If you don't have access to those, look at the real estate section of the local news paper. Look for someone who is listing a lot of the type of property you want to buy. If they are listing a lot of that property, they probably have some expertise in that area.