If you paid for the room, you enter it as if you made a cash donation to the charity. If audited, you would need a letter from the charity saying something like "Thank you for donating a weeks' accommodations at _____." The letter does not have to prove the price, you do that from your own records. But you need proof that the donation was accepted by the charity and the costs were paid on behalf of the charity.
If this is a hotel you own and you gave away the accommodations for free, you can't deduct anything. Your tax "reduction" is the fact that you have less taxable income to report. OR, you can book the revenue as if you received it in cash, then deduct the same amount of cash as a donation.
You can deduct out of pocket costs that you paid in order to provide the room to the charity, but I don't know how you would reasonably prove that a few dollars of the maid's salary was allocated to this specific room, or any other hotel staff or utilities, etc.
