How to make money on YouTube easily?

I am in University and want to earn some extra bucks by posting money on YouTube in my free time. I am not looking for a full time income, just few extra bucks to pay my internet bills.

So, whats the easiest way to earn few bucks on YouTube, without investing much time.

I tried posting small Movie clips (4-5 mins) after seeing many other people doing the same, but found that those videos cant be monetized, as they are copyrighted.