people only get used when there is dishonesty and the other person isn't there for you like you are them and you aren't there for them in the way that they want i guess. i don't really know the exact differences in those ways. i think feelings distinguish relationship and friendship.
The other person is taking more from the relatioship then they are putting in.
every human being knows , it just come randomly the feeling thing i mean :P
You can only evaluate people by their action. You cannot know what is in their heart. Fact from emotion. Then you will have a good understanding.
It's simple. People come to you and ask you the exact same questions every time. But then they ask what they really came to you for. Sometimes they don't even wanna know how are you.
At the same time you cannot ask those people the same things because you don't really want to be friends with them. You are just being nice. People take advantage of you for being nice to them. It happens all the time. I am talking about "friends".