We are a big fan of books and movies (mostly DVD but our Blu-ray collection is not small). We've been accumulating a lot of them over the years, so I had to invest in two cabinets to put everything away.
When we moved, we decided to sort through our books, CDs, DVDs and children's video games.
Sorting itself is rather easy: on the one hand, what I keep, that is, everything we do not intend to part with, even if we do not use it regularly. On the other hand, everything I know for a fact that we will no longer use. The games my children haven't played for years, the books I've read and I don't intend to reread, the DVDs we never watched, etc..
The hardest part is finding a "responsible" way to get rid of it. I know one neighbor who threw it away, I could have followed suite and thrown everything in the trash, but I didn't. Not only do I have a hard time throwing away useful items, but they are all in good/new condition and can easily be used by someone who would actually like to have them.
Fortunately, the Internet is there and sites like ebay and co. allow you to resell anything and everything quickly and easily.
I started by opening a shop. It's simple, just log on to the site, create an account and enter the item for sale.
In case of sale, the site takes a small commission on the sale price and pays you.
Outside of the Internet, there are stores that take back unnecessary items and resell them: thrift and second hand stores.
By combining all these solutions, I managed to get rid of all content that cluttered the library and, by the way, we even recovered some money that we spent on obtaining it in the first place.