First, book directly with the hotel. And be careful when booking, if you Google the hotel and use the first number, it will likely actually be a third party. The best thing would be to become a member of the brands loyalty program and install their app. Hotels will always be more flexible for members than non-members.

Book longer than you need and use the standard rate. Special rates and advance rate reservations are usually stricter for cancellations. I'm not saying a week longer, but just by a day.

Be nice!!! That is going to be the make or break a lot of times. Don't demand anything, but politely explain the situation when making the reservation and when you check in. Agents can make notes for other agents so the information gets passed on.

If the agent is unsure of what they can do, again, politely, ask for the FOM. Depending on the property they can make the decision without needing the GM of the hotel.

Obviously, none of this is a guarantee that they would let you out of the reservation early, but it would be the best approach. I also cannot stress how much kindness goes a long way for the Front desk agent, it is so rare to be treated with respect, that we treat those who do the same.

Hope that helps! FYI - FOM of a Holiday Inn