What do you say when you ring up or reply by email in response to the ad?
“Hi, I’m writing / ringing about the room advertised on flatmate.com…”
Be sure to give a brief background of yourself like current employment, when you can move in, and any real estate references you may have.
If you don’t have real estate references, it may be worthwhile speaking to recent real estate agents to ask for a reference. It could make or break your application.
If you get knocked back, don’t take it personally. They are obviously looking for someone in particular, and you just don’t fit the bill!
If you do need to inform people that they weren’t successful, it might be worthwhile setting up a temporary email address for all correspondence. That way it makes it less of a need for it to be someone’s responsibility. No one like to be the bearer of bad news.