If you're using WordPress, then there should be an option somewhere to disallow indexing. (Sorry - I don't use WP and can't be more specific.) Otherwise, a robots.txt file with
in the root directory should be enough to stop any reputable bot indexing the site.
I read somewhere that Google likes to be mentioned by name, but I can't remember where I read that* and don't know how true it is. However, I always add the extra line, just in case.
I've never had any problems with that.
*except that it was a source I considered reliable at the time.