I think we just have to try our best. Expanding our view to include our perception of others feelings I think is important. Though we can never be 100% sure what they are thinking or how they really feel once you know a person a while you can get a feel for them and guess. I think asking them is really important because it avoids confusion, but as Byz pointed out it can never be sure. Because everyone lies sometimes, sometimes without meaning to and sometimes even to themselves.