Just starting the process (VERY slowly with my craft stuff - I've got about 18 years worth). Just finally got rid of a ton of my kids' too small clothes to friends who have really small kids. I have a bunch of my clothes to go through, as well as holiday decorations (that never seem to get put out - or even found until the holiday is over for the year!)
With my crafting stuff, I've really narrowed down my likes and dislikes and honed my style. I've gotten much more careful about how much and what new stuff I bring into the house. Because I don't have a dedicated craft space yet, my supplies have been all over the place. I'm about done finally getting everything in one place (still several places in my house, but all ribbon in one place, all punches in one place, etc.) so I can finally see everything I have. I make cards and items for friends and family so I'm not getting rid of everything that's not my style because my style certainly doesn't apply to my friends and family, but I've narrowed down what new stuff I want/need to fill in gaps. I now make a detailed running list of anything and only buy items I have a specific need for and will be used for a definite project. Once I really get going, I make major strides, but it's the getting going part that's always the issue ("once an object is at rest, it tends to stay at rest" type of deal). I've got several teachers who are begging for various supplies, so once I get through my items, I don't have to worry about what to do with them to get them out of my house.