Steve Dion has made a good suggestion. Another site you may want to consider is texas sailing which does a lot as well.
If you go to Yachtworld, it will list all the dealers that are in that state and you could look them up. You can look at their site and see what is sold and monitor it for several weeks. If you see those listings disappear on a regurlar basis, then they are selling boats but if the listings are constantly remaining, then be careful. Word of mouth is of course a good source and I am not sure but why not check on Angies List. I do trust this website as a source and Texas Sailing as well.
If you list on graigs list, make sure you have the money in the bank before you turn over the title work and there are third parties whom you can use to hold the title work and turn that over when the monies have cleared as I have come up with scam artists on that site in the past. If wire transfere, make sure you open a new account just for that and then remove the funds immediately and close that account unless the bank specifies no monies released without your express permission which I used when selling boats overseas. I hope this helps you.
crazy dave condon