Despite all the suggestions you will read in this thread
Unless you live in a very poor country, the fastest, easiest, and most convenient way to obtain bitcoins is to buy them.
This is the wisdom of the day. There's no secret to earning bitcoin. Bitcoin is currency. How do you earn money? Do that...do it better than you do it now...do it more often or for more money or for more people. And then ask them to pay you in Bitcoin.
It's that simple.