In the uk and the us,it's important to behave as if everyone is your friend.but this does't mean they'insincere.what's important is to read between the line.is the person just being polite, or do they really mean it? If someone say 'let's meet up next time you're in London ',they are probably just being polite.but if they give you their phone number and tell you to call them,then they really mean it. Remember:sometimes people are nice to you because they like you!