how do you deal with strangers who act like they know you

[c=003BB2][i]in real life? people who act over familiar with you, when you don't know them and they don't know you?

i really dislike it when i encounter that, as i am a private person and take myself seriously as well, and don't like it when someone that i don't know, who doesn't know me- acts familiar.[/i][/c]