After spending the last few months basically touching everything we own, I can share how we made our decisions.
If something would be useful to one of us (myself, my husband, or my daughter) in the near future (so not something that a potential grandchild would use), we saved it. If it is used everyday, it went into our new small apartment. If not, it was boxed in plastic containers and went into our storage unit (stuff like holiday decorations).
If it held really strong sentimental value to one of us (photos, old yearbooks, old family jewelry, etc.), it was kept. Again, the most “priceless” in terms of value to us (old family photos, etc.) are in the apartment and all the rest is in plastic boxes in the storage unit.
If it could be used by somebody now (good condition, good use), it was donated to a rummage sale, charity bin, local library, or a refugee organization. This included most of our furniture (we had already furnished our new apartment), kitchen wares, linens, toys, puzzles, games, etc. Old books went to a collection bin that benefits a local church (they take any book with an ISBN no matter the condition)
If it was electronic and out of date, we brought it to the town dump (they collect for recycling of some kind). I made sure to drown or smash the hard drives. This included TVs, computers, printers, etc. I was also able to take to the dump old metal stuff (like broken outdoor furniture) and expired fire extinguishers.
If it had immediate value, but we had no interest in it, it was sold. This included jewelry, collectible coins, old DVDs, outdoor furniture in good condition, an electric piano, etc. I didn’t make much on this, except for some very ugly Italian gold chains that netted me over $1,000. I also failed on this in not being able to get anybody to buy an old Movado watch. (Still hanging on to that).
When all else failed, the stuff went to a junk collector or out with the trash (our town really limits the amount you can put out - only two bins a week -so this was challenging). I really tried to minimize this group of stuff, but some things were just too old, broken, or unwanted to do anything else with.
What we did may not work for everybody, but it worked really well for us. After going through this process, the entire family feels freed by not having all this stuff around us. We have not missed anything we got rid of. My daughter even thanked me for doing this now (so she doesn’t have to do it years from now).