At all times talk to the site's existing users using the communication means they most expect you to use.
I had possibly my worst experience on the net in autumn 2000 when one expert answers site was taken over by another. My correspondence email address with the answers site on which I was an expert was a Y! address which was banned at my place of work (and at that time I did not have a computer at home).
This didn't matter, because whenever the answers site communicated with users and experts it did so through the account interface on the site itself.
However, when the site - which was very good - was taken over, the new (and rather inferior) answers site apparently did not know this and sent two emails as notification of the takeover.
The first I knew of it, the site I had been an expert on no longer existed, the format was wiped out, my account was gone and all of my answers (about 70 pieces of research) and user feedback was lost.
When I sent an email to the new company, I received the reply:
"Well, if you don't check your email, what do you expect?"