In addition to prompt reporting of claims, you must "take all reasonable steps to protect the covered property from further damage, and keep a record of your expenses necessary to protect the covered property." For instance, if a tree falls on your building and exposes your personal property to the elements, the insurer expects you to minimize further damage by any means possible. This could include moving your property to another location, or having the building damage temporarily fixed to prevent further damage until the adjuster can make a determination of damages.
It is the adjuster's job to set the reserve. A reserve is the probable ultimate exposure. In other words, it's the amount the carrier expects to pay for the claim. The better the information they get, the more accurate the reserve. Reserves do change from time to time that is why it's imperative to pay close attention to your loss runs. For the difficult claims, your agent should be scheduling (and attending) claims reviews with you and the adjuster. This gives you the opportunity to question how the claim is being handled and have the adjuster justify the reserve.
Hopefully you've done your best to prevent claims from happening, but we know they do occur. It's what you do when a claim occurs that determines the final payout. It all starts with reporting all claims in a timely manner. A good agent, and insurance company, will guide you through the process, and do all they can to make sure the process goes smoothly. If they can't, find someone who can.