The best way to create a thorough inventory is to physically walk around your house from room to room and build your list. Take pictures of everything, including serial numbers and receipts where you can. For each item, try to include a description, when it was purchased and an estimated value.
There are a variety of tools available to help you. You can simply write everything down in a notebook, create a spreadsheet (Microsoft Office has templates online), or use one of the new inventory apps on your computer or smartphone. The Insurance Information Institute and the National Association of Insurance Commissioners offer free apps with secure online storage. Many insurance companies have their own apps, as well. The best tool is the one that you will actually use.
Creating an inventory now isn’t difficult, though it can be a little time-consuming. But it is well worth the effort, and if disaster strikes, you’ll be thanking yourself later.