A while back I thought of selling my Ibanez RG 470 and aside from being a little out of tune it's in perfect condition. The guy in the music store offered me $50, I laughed in his face.

My suggestions are e-bay, or take an ad out in a local paper. Craigslist has a for sale section that might be worth while as well. I also looked at your profile and noticed you're 16 or so, why not put up a flyer at school?

Either way you'll likely get a better deal if you sell it yourself than take it to a music store ;)