crap

It depends on who it is. If it's a relative or someone from work who deserves your respect then, yes, you should just listen patiently but if it's just someone you know or someone from off the street, it's okay to suddenly remember that you are late for an appointment and get the heck out of there!

Well, begin by listening patiently. The other person may say something worthwhile, or it may turn out to be crap. Sometimes crap is worth listening to for HOW it is said, or so you can learn what's wrong with this particular crap. (This will save you time the next time you hear the same crap.) But, there is no need to overdue the patience part. Get out of the coversation if you want to (how politely you do it is up to you and depends on how you know the other person.) How much should you listen to? Remember: "Keep an open mind, but not so open your brain falls out."

To know whether that is crap or not you have to listen them . right? other wise how you will decide that is crap or not? You may say that at the beginning of topic only it come to know its crap. But what if That person intention was to tell something which of out of topic as a example to that topic(Which you call as crap) and then come to main topic. So i think you should listen other fully. After that person end if he told really crap then you also say something crap and keep quite. So that he can come to know his mistake.