The next key is e-mail. This is the easiest way for you, through your site, to respond to your readers. It is the universal language of the Internet. Another key is get personal. Use your name, and use your readers name.
Nothing is more powerful than personalization.
Make responding and following up to your email a priority. Nothing should be more important than responding to your email. The most exciting and cutting edge site on the web will fail miserably if you don't respond to your email promptly. Automate as much as possible. Make it easy for your readers to get and respond to your message.