to know the ropes is generally to know how to do something or how something is done. It's idiomatic, but I don't think it's a cliché.

Others have answered this, so I will simply explain to you what "cliche" means. When something is cliche, it means that it is overused or overly expected. Below is a link to a brief article I just found that might help you tell the difference between "cliche" and "idiom". http://esl.about.com/od/vocabularyreference/a/v_cliche.htm

It is NOT a cliche. know the ropes = know all about something

Yes you are right. " To know the ropes"= to be familiar with something. Example: If a new person arrives at work, the manager will introduce that person to someone in the company 'who knows the ropes' and can help him/her.