PBS has an interesting way of decluttering in the Legacy List series. The service asks for 5-10 mementos to (find and) keep. Everything else goes to resellers, charity, or garbage. They often choose large estates that have been in the family for a century.
One bit of advice I took from an old decluttering book: You can only sentimentalize a limited number of things, so any mementos of yours beyond what are displayed on a single set of shelves should be stored/rotated or discarded.
