To become ambassador, what it takes is the ability to fork over 150 USD, to fill in a form here: http://www.ichotelsgroup.com/h/d/pc/...mbassador.html , and I guess it also requires a postal address to receive your ambassador kit

To become RA, there are presumably no fixed rules, however consensus seems to be to stay at at least 3 InterContinentals and spend at least 50 nights within one calendar year at ICHG properties. It's no hard and fast rule, however, only ICHG knows for sure.....(e.g. I routinely stay at >3IC and >50 nights at ICHG each year, but have not been "upgraded" to RA despite this being a pattern for a while...)