Most commonly, they use "lorem ipsum" text, which is nonsensical copy that, at first glance, looks like Latin.
Meaningless text, oddly enough, is quite important in design work as it encourages the client to focus on the design rather than get preoccupied with the written message. And, generally speaking, this works, although we did once have a client who rejected his project's initial artwork because he "doesn't understand Latin"!
We've seen passages of lorem ipsum text so often that you can only imagine our delight when we discovered some more entertaining alternatives!
Movie legend Ipsum
Select from one of four well known Hollywood A-listers and get filler text based on their best film scripts. picksumipsum.co.uk
Business babble Ipsum
Corporate Ipsum generates passages of impenetrable business babble, so we'll be using this on all corporate design projects from now on cipsum.com
TV themes Ipsum
Our favourite, however, which will strike a chord with anyone who grew up in the eighties, is TV Themes Ipsum (malevole.commv/misc/text/) which uses scripts from well known TV shows as the source of its filler text. So when you get proofs for your next design project that include the following, you'll understand why:
"Ten years ago a crack commando unit was sent to prison by a military court for a crime they didn't commit. These men promptly escaped from a maximum security stockade to the Los Angeles underground. Today, still wanted by the government, they survive as soldiers of fortune. If you have a problem and no one else can help, and if you can find them, maybe you can hire the A-team."