Disclaimer: I've carried a bottle of Bisleri ONLY ONCE while visiting India. I had consumed some heavily poisoned chicken curry and before the attending doctor could say "E.Coli", I was squirting fluids out of all orifices at once. Fantastic pressure too. So as soon as I gained a hint verticality, a mineral water bottle was thrust into my hands.
My mother says the clothes are a sure giveaway. Others point to the much-maligned Bisleri bottle, or the alarming habit of saying "howzitgoin" to the milkman, the maidservant and the newspaper boy.
What are we talking about? Identifying an Indian visiting India. Hmph. (link to Churumuri)
Sure, some of it is stereotyping, but it is funny and true. Not so funny is the comment thread (at the end of the linked post), which, predictably, devolves into a dull India Vs. the West debate.