In case you don’t want to spend too much time with any Drupal chat / support system configuration and development, you can use some external application. Advantage of this solution is, that it is faster to configure and all perfomance needs handles external server. Disadvantage is costs, of course.
But, it is easy to calculate what is best for you.

In last time I spent much hours with helpdesk tool, which I really like – Live Agent.

Therefore I decided to develop Drupal module for this excelent application that combines live chat, helpdesk and offline support in one.

All installation takes about 5 minutes. You need just create trial account of Live Agent and then download and enable module on your website.
After login to Live Agent panel you can enable preffered button and start to support your clients.

HTML knowledge is not required!