I maintain two twitter account for my sites, but Warren is right, it is very hard to maintain the proper amount of engagement to make it work. For me I was able to use one for my mobile casino website using my phone and tablet, and another for my main website from my home computer.
Its nice to have the separation of the two, but anyway… I am struggling to keep up on all of the social networks, and find that even taking one day off can put me behind on them.
As far as best practices. Put your homepage in your twitter description, as well as a few decent words about your site and what it has to offer other people. When your account becomes successful, this will help your follows find your site. I’m sure you know that kolo, but I though others may not. 