Right and Wrong

Have you ever asked yourself whether you are a good person or not?  How do you really know if you're a good person?  I mean, just because someone does something like volunteer to help the homeless on a regular basis, or goes on mission trips every year, does that make them a good person?  Or does that just mean that they have too much time on their hands and don't have any better way of spending it?  What if they do things like this all the time, though?  What if all you see one doing is good things?  Are they a good person?  What if while they are doing it, they are thinking really bad thoughts?  What if, when they are alone, they are doing unthinkable things?  Are they a good person, or not?  What if they don't know that what they are doing is wrong?  Then are they a bad person, or are they just naive?

Most people have enough common sense to generally know what is right and wrong, but what about the things like this:  Telling someone who is talking crap about them, or telling a friend if you think their boyfriend/girlfriend was flirting with you/someone else. 

Is it right to say, "hey, (so and so) was saying (this) about you."  Should you tell them and let them know who they should be telling things to, or should you just say, "hey, I overheard someone saying (this) about you."  Either way, aren't you hurting someone?  Either someone is going to probably lose a friend because of you, or that person is going to keep getting talked about.  Should you get involved at all, or is it really none of your business?

What about telling your friend about their boyfriend/girlfriend flirting?  What if you just took it the wrong way?  But then again, what if they really were flirting and they end up cheating.  Then wouldn't you feel guilty?  Which is right?