Do Indians shake their heads to say yes?

What is the most common way for a westerner (or NRI) - who has probably visited India once or twice - to act knowledgeable about India? Just reveal to the audience (mostly firangs) that, in India, a person shakes who his/her head side-to-side is really saying "yes"!!!

Only problem, I - who have lived all my life (30+ years) in India - have never seen this happening.

I wish these firangs and NRIs please give up this silly - and untrue - characterization. Thank you.