The re-opening of hotels will likely be gradual, done by risk assessment, and it will probably include many restrictions

By the way, this list is based on the scientific process of baseless, wild speculation, while waiting out the quarantine.

Re-do your shift schedule for different % of the usual business. In other words, one schedule each for 30% of last year's business, 50%, 80%, etc. You'll be able to explain to your staff why they are getting only a fraction of last year's hours.
Research which food costs will increase when you order less volume.
Move kitchen stations (if at all possible) to create more space.
Create a re-opening menu with items that limit the number of cooks in the kitchen.
Front Office/Reservations
In expectation of occupancy restrictions, add "Covid19 Out-of-Order" designation in your PMS system. These rooms will be tracked differently than regular OOO rooms.
Decide which rooms you will take out-of-order to ensure social distancing and limit elevator use.
You may have to read the temperature of all guests when they check-in so decide on whether that will happen at the front door or front desk. You may want to start writing an SOP for this.
Start talking to your GM about the possibility of requiring a Covid19 affidavit to be signed at the front desk where guests confirm that they have not been close to anyone with virus symptoms.
Start crafting a Covid19 disclosure for Phone Reservations to read to each guest and to post on the website (with an electronic "Agree" button).

Add a new line for "Covid19 Out-of-Order" rooms to your Pace, Forecast, and Yield reports. This will allow you to better compare Year-over-Year results this year and next year. If you bundle all the OOOs together you will affect the variances.
Find alternate years to Pace against, maybe 2009. All Pace reports will be negative this year and positive next year so you have to put the number in a different context.
If there are occupancy limitations, you may be sold out every night, so you have to find alternative metrics to track the strength of the market. Try putting together data from your POS or CRM to track KPIs like average guest spend for all outlets year-over-year.

Establish process for changing room access and locker distribution for social distancing.
Simulate common area distancing scenarios, furniture distribution, common bathroom usage rules.
Do you allow access to the pool by reservation only? If you do, you will need a process for that.

Practically every page on your website will need a pop-up advisory so might as well start loading those now.
Compile "Best Guests" list from your CRM to send personalized messages. A simple email blast will be lost in everyone else's email blast.
Redraw your meeting space floor plans for social distancing requirements. Load the new floor plans to your website.

Publish your temporary limited menu of spa services.
Determine bag handling procedures. Is the bellman allowed into the rooms when they are exposed to common areas of the hotel?.

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How Each Hotel Department Can Start Preparing for A "New Normal" Re-opening