If possible, value the property you report at its acquisition value. If the property was purchased by your ward and you know the purchase price, use that.
If you are unable to determine the value at the time of acquisition, you may have to use the current market value. For some types of property this may mean you will need to obtain an appraisal or research the value. For example, if you were reporting the value of an automobile, and you were unable to determine how much your ward paid for it, you might consider researching the value by typing something like "used care prices" into an internet search engine and then use one of the services online that specialize in determining current prices for used cars. Keep a paper copy of whatever you do so that if it ever becomes an issue you can provide your method of valuation to the court.
The value that you report will be used as the value in each of your future accounting reports until the property is sold or otherwise disposed of. This means that as long as the estate owns the property you will not need to adjust the value you report.
At the time the property is sold or otherwise disposed of you will report any gain or loss to the value of the property. That is, in the accounting report covering the sale or disposition of the property you will show that the property is no longer in the estate and then report such things as the receipt of cash, cancellation of debt, or acquisition of other property that resulted from the sale or disposition of the property, if any of these actually occurred.