Go to the specific hotel's website.
Locate the "Contact Us", "Customer Support" or "Inquiries" section of the hotel's website. Find a link you can click on that is somewhere along these lines. These options will usually be at the bottom of the website.
Fill out the form the hotel has in place for you. Larger hotel chains will most likely have this form so that your question will be answered quickly. Sometimes, the hotel will just give you the e-mail address for you to send your question to.
Keep your inquiry short and to the point to get your message across. Use formal language when writing out your message.
Obtain the physical address of the hotel by referring to the website, or by calling the hotel and asking.
Write your letter in a professional manner to the hotel you want to send an inquiry to. If you want to be contacted, leave your contact information at the bottom of the letter.
Address it properly. If you're unsure on who you want to send the inquiry to, call the hotel and ask. For example, if you're writing about the housekeeping services, ask for the housekeeping manager's name.