Keep all receipts. Take pictures of everything. Catalog each item, update insurance company as to inventory and keep the inventory in safety deposit boxes. I do this for my jewelry, electronics, gold coins/bars, etc. Anything of value is catalogued.

I keep my diamonds in the safety deposit boxes along with my gold and irreplaceable items (photos, stock certificates, bonds, autographs, etc).

I keep backup data discs in several locations. Never lost one file!