Having any receipts for stolen items would be ideal. This is an excellent way to prove ownership of the items on the insurance claim. If it is not possible to have receipts for any or all of the stolen goods pictures are the next best option. Pictures, with dates especially, are another great way to prove ownership. Create an inventory list of missing items to submit to your insurance company.
To prepare for any possible future losses it is recommended to take pictures around your home, taking special note of bigger ticket items like electronics, jewelry, tools, and so on. Keep these photos stored safely in multiple locations, for example in print and also on a computer storage device, so they can be easily accessed if needed. Another idea is to create a video of the items in your house. Keep the video in several locations as well as a backup.