In the case of my books, it is a very slow process, though I have the equivalent of 4 shelves of books that I expect to part with after I actually read each one. Sometimes there are surprises, and I hang onto a book after all, or I get rid of a book that is from my main bookcases (the last one I recall is Elizabeth Bowen's The House in Paris, but I'm sure there were others and there will be more in the future). Normally, I simply donate these to the library (for sale, though if it is fairly rare I offer it up to Robarts and they actually took 4 which should make their way into their collections -- so cool), but if the books are in particularly good shape I sell them at BMV. I feel slightly more in control than I described the situation here, but I still have an absurd number of books in the house.
I've had a lot of success selling pop/rock and jazz CDs at BMV, though probably for slightly less than I would get elsewhere. I'm not quite sure what to do about the classical. I thought I had found a place, but I've been given the runaround (usually the owner says they don't have enough cash after paying the rent and I should call back in a few weeks!) and the same thing happened yesterday. I'm pretty tired of this, so I'll take one more look through the options and take them someplace else. BMV would probably take them, but I'd like a bit more money for them. I've found that trying to sell on Amazon.ca just isn't panning out that well, but the shipping costs to the U.S. are such that I simply can't afford to sell on Amazon.com unfortunately.
There is a book sale at the school and I am donating just a few adult books,* but we are taking the opportunity to go through the kids' books, primarily the books for younger readers, which are in my daughter's room. It was interesting watching her decide which books she was done with. I think she hung onto quite a few mostly because she remembered our reading time together or in other cases she just isn't ready to give them up and effectively give up on her childhood, essentially moving up into the preteen slot. Yet when we get books from the library, she is usually looking for longer, more challenging books, and she often likes reading non-fiction books, particularly on science. I should probably remember that on my (very frequent!) trips to the library. She's actually becoming quite a good reader, though her spelling isn't as good as her brother's. (While overall we do prefer the school system in Toronto to than in Vancouver, our son's teacher in Vancouver did have a more rigorous approach to spelling with regular quizzes. Teaching spelling seems a bit more haphazard in Toronto, but with a greater emphasis on math, which is an acceptable trade-off in my view. I know we should be doing more at home with her on spelling, though I am already spending a fair bit of time practicing French and math, and fortunately she is enjoying math.) To return to the main topic, I didn't purge quite as many books as I had hoped, but it's a start.
* Books primarily aimed at adults. Get your mind out of the gutter...