Under pressure to create (usually against a deadline), a writer will naturally use familiar verbal patterns rather than thinking up new ones. Inexperienced writers, however, will sometimes go further, and string together over-used phrases or even sentences. Consider the following example:
When all is said and done, even a little aid can go a long way in a country suffering from famine.
The argument is commendable, but its written expression is poor and unoriginal. First, consider the phrase "when all is said and done." Once, this phrase was clever and original, but so many millions of writers and speakers have used it so many times over so many years that the phrase has become automatic and nearly meaningless. This type of worn-out phrase is called a catch phrase, and you should always avoid it in your writing, unless you are quoting someone else: you own, original words are always more interesting.
A particularly stale catch phrase -- especially one which was once particularly clever -- is a cliché. In the example given above, the phrase "a little aid can go a long way" fits into the formula "a little *** can go a long way," seriously lowers the quality of the writing. Essentially, a cliché is a catch phrase which can make people groan out loud, but the difference between the two is not that important -- just remember that neither usually belongs in your writing.
Here are some more sample clichés and catch phrases from students' essays:
the dictionary defines *** as ...
key to the future
facing a dim future
drive a wedge between
enough (for ***) to handle
in today's world
the *** generation
the impossible dream
enough to worry about without ...
putting the cart before the horse
a bird in the hand
glitzy, high-tech world
There is no simple formula that you can apply to decide what is a cliché or a catch phrase, but the more you read, the better your sense of judgement will become. Remember, though -- if you think that a phrase in your writing is clever, and you know that someone has used the phrase before, then you are best rewriting it into your own words.
Special Considerations for Catch Phrases
While clichés and catch phrases have no place in academic essays, there are some times of writing where you should use pre-existing formulas. Such documents include scientific papers, legal briefs, maintenance logs, and police reports (to name a few) -- these are highly repetitive and largely predictable in their language, but they are meant to convey highly technical information in a standard, well-defined format, not to persuade or entertain a reader -- creativity in an auditor's report, for example, would not be highly prized.
On the other hand, catch phrases are not appropriate in less technical areas. Journalists, especially, are under a pressure to produce a large amount of writing quickly, and those who are less talented or unable to meet the pressure will often end up writing entire articles made up of over-used catch phrases like "war-torn Bosnia," "grieving parents," or "besieged capital."