A pre-prepared contents inventory should be accepted by most insurance companies and you should keep it updated. Insurance companies may require the inventory be placed on one of their forms. Insurance companies may also require receipts or other documentation of ownership for these items on the inventory, especially higher dollar items. Check your policy language. Some adjusters will give you forms that they say are "required" when they are NOT required by your policy. Most policies I've seen, only say they need a description of the item, when you bought it, the replacement cost of the item and the amount of depreciation. With digital cameras so popular it would be easy to make a photographic diary of the contents of your home. After the photos are taken - burn them onto a CD. You could have several directories on the CD for instance - furniture - silverware - furs....
The best way I know of is to engage an independent third party professional Appraiser to inspect, identify and valuate your property. Then when you make a claim, if you ever do, there is professional evidence in your favor.
It is really helpful to have an inventory, but in the 100 or so Personal Property claims due to fire that I have worked, only 1 person had a pre-loss inventory. Its something people always think of AFTER they need it. At least take a few photos. I recommend 5 per room as a minimum, and use more in the kitchen, or any room that has cabinets.
There is a section on my website which goes further into the pre-inventory process, and how to do it.