"Siemens codes (SIE / 7346) are among the most reliably active corporate codes, showing 15–22% discounts at many global Marriott properties. The code appears in widely distributed PDF documents traceable to 2014. If you are caught, the property can raise your rate to the current rack rate and you could be considered to be defrauding the property. Wide documentation suggests this code has been in circulation for over 10 years."

"I have been asked to show some proof couple of times. I normally show my corp id but credit card with employers name on it has worked, too. As would probably just showing my laptop with employer e-mail account or whatever. My impression has been they are happy with just about anything that proves I'm working for the company whose rate I use and why wouldn't they."

"I don't do mobile check-in if I'm wanting to upgrade. I check the app before I go in to see if any suites are available to book during the duration of my stay. If there is I just say "Would it be possible to get upgraded to an available suite with my platinum benefit?". Of course this is typically at the hotel that I stay in about once a month for 3 day at a time for work. The front desk pretty much knows me and know that I am fairly low maintenance."