Start with high-value categories
Major appliances, electronics, furniture and other significant items can be documented before smaller possessions.
Use photos and identifiers
Model and serial numbers can help distinguish similar products.
Store a protected copy
An inventory is more resilient when a copy is not dependent on the same device or location as the items themselves.
Update gradually
Adding major purchases when they arrive is easier than rebuilding the whole inventory every few years.
General household information only. Follow product labels and manufacturer instructions. Electrical, gas, structural, hazardous-material and other safety-critical work belongs to appropriately qualified professionals.