1. Know what the inventory is for
An estate inventory is the schedule an executor works from: the contents of the house, described well enough that someone who has never been there could identify each thing, with a value against whatever carries one. The same list does a second job for the family — it is the shared record of what has already been decided, so the sorting-out can be split between people without anyone losing track.
What the courts require of you differs by country, and the solicitor or registry handling the estate will tell you which assets must be listed and which need a formal valuation. This guide covers the practical half: getting an accurate, photographed list of a whole house built quickly, in a form you can export when the paperwork asks for it.