One suggestion I have is, if it is convenient for you, to try the Shakopee one first. I live closest to the Burnsville one, but I like the Shakopee location a lot more. Even with gas prices what they are, I will go first to Shakopee, then take the left-overs to Burnsville. Also, Shakopee has a frequent buyer/seller card, I believe.
They buy what they think they can sell, so you have to work with seasons. Call ahead and see if they are still taking summer clothes or if they are starting to take fall and winter items and what hours they are buying the things you are selling. Also, brands from discount stores (i.e. Circo from Target) are less likely to be taken than name brands. Almost anything with stains (even small ones) or pilling will be rejected.
Finally, if you are looking to sell big ticket items like strollers, check their inventory first. If they have one virtually identical to yours selling for $20, chances are the previous owner got $10 for it. It's a good way to decide if it's worth your trouble to bring in the big things.
Hope this helps.