First, identify your passion or what can you do to earn Bitcoin. Just like @mk4 said, you can work and get bitcoin as your salary or payment.
You can also do buy and sell, you buy some things and sell them for Bitcoin with profits also.

Just last week, someone paid me to do some minor task for him/her website; (Completed by GreatArkansas) Looking for Node.js (express) coder, thanks to @Raja_MBZ .
It's kinda pretty awesome, I found a way to earn bitcoin by what I am doing or passion in life; coding or developing some web app.