Earning bitcoins includes various methods from faucets to trading to mining to signature campaigns.
Here's what they offer and which one i prefer myself.
First, faucets- they pay equal to almost nothing. They just promote new comers in bitcoins and nothing else, it's safe because of zero investment but it's too much low paying. It's worthless.
Secondly, trading - now payment here is variable, you may get loss or profit depending upon rates.. It's risky as it involves investment.
Thirdly, mining--  Mining involves large investment and pays high too, but you may get loss depending on certain factors..
Fourthly, Signature campaigns-- No investments needed and it's pays high too. No problem of loss..
According to me, signature campaigns are best , as there isn't investment and no problem of getting loss. You get paid for your work.