Although the CREW manual is now part of the Internet Archive, since the person responsible for "retiring" it from the Texas library association that had it available has not been pilloried for it, it does an excellent job of explaining the weeding side and providing a method of making sure you don't get into the position where someone starts shrieking about mass discards unless there's real political bullshit afoot.
Jessamyn's still right, good comms on weeding are necessary.