What everyone else said. Now that others have covered the basics and the legalities, I've got two personal suggestions, from recent family experience.
First, try to keep everyone from getting emotional about stuff they want to keep. You gotta want to keep it enough to be willing to devote X number of square feet to it until you decide to get rid of it.
Second, DON'T, for the love of god and all that is holy, decide to "gift" any younger and less established relatives with things you all are too attached to to toss out but not attached enough to keep for yourselves.
My in-laws' home is over-crammed with the furniture they couldn't let go of. My home is also crammed with the furniture they just couldn't get rid of. Actually, at this point, I put my foot down after literally tripping over too much stuff too many times and now most of it is in the garage, waiting for my spouse to get around to renting a truck to haul it to the dump. From talking with my probate clients, I gather that this is a pretty common phenomenon. Probably not as much now as when the owner of the stuff dies, but it seems to still happen. Get rid of it. It really is a lot easier that way.
Yeah, I know the op didn't mention this. Consider it a PSA from hard experience.
(And I swear my FIL's head will explode if I ever toss his mother's big, elaborate antique dresser that I hate and that is not child-appropriate, currently relegated to our basement until our three year old is big enough to be saddled with the thing. I just hope she has the guts to toss it when she's old enough.)