I like perusing Buffalo Exchange, but, whenever I bring some clothes in for store credit, I end up disappointed. They seem to give you very little credit for good items, and they are very picky. So I clean out my closet, take it to Buffalo Exchange, and come back with 3/4ths of the stuff. Discouraged, I set it on my floor and it sits there making my room dirty for months.
I would suggest going in to trade during an off time (not a weekend) when there will be less people trading. They may spend more time looking at your items. They also prefer the items to be in season, so don't clean out your sundresses until May-ish if you don't want to have to bring them back home.