there are a lot of topics here in this section about how to earn bitcoin, search and you will find a lot of ways.
here is a summary:
1) offering your skills in return for bitcoin >> best way and highest payment
2) trading >> this is good, with risk but good earning
3) signature campaign >> low pay out
4) faucets >> waste of time
5) many people mention gambling but it is not a way of "earning" money it is "spending" money