You earn bitcoin by some assignments online.
But the most easiest i think is by campaign signature.
Or one can even earn bitcoin with bitcoin faucets.
Yes, joining in signature campaign is a very good choice to earn money compared to faucets around it will make your time wasted, also render some service that you can, putting your skills into something worthy of some coins. Those who have skills can never be dependent on others as they can always earn using their skills.
i think both is better signature campaign and faucets i also earn bitcoin from these both but i think signature campaign is not regular way to earn bitcoin when signature campaign closed then i earn bitcoin from faucets.