To start with earning money online you have to make one important decision to make:
Do I want to put money in it?
(There is a high risk of loss!)
Or do I only want to make profit, but work a bit harder?
If you decide to invest some of your money, the more you will earn.
There are multiple ways of investing and depending on what kind of work you prefer you can make things easier(and increase your earnings!).
If you don't want to invest anything there is also a way to earn online.
But this is only possible with paid to click(ptc), paid to read(ptr), and Paid to read mails(ptrm) and surveys.
I think you have already guessed is, but the most profitable, revenue share, requires investing.
Depending on the site you use there is an minimum amount to invest.
If you would really want to start earning online, the best thing to do is just try it.
Become a free member at some sites, mail with administrators and look for people who want to answer your questions.
This is just to get known with how it works and you hear opinions from different people, which is always good.
After some time you could decide if you would want to continue this.
Maybe you trust a certain site enough to invest some or you stop using another site because of your reasons.
Be Very Careful When, Where and How you invest money! There is a huge risk of loss, and it is your own choice!
And because it is internet some parts are based on trust.
Until you get your first payment don't expect anything, there are people/sites who like framing others.
Well, back to the main subject.
After you have watched and tried a few sites you can decide to invest.
Usually you have got an idea of what way of working you like most: Ptc, Ptr, Ptrm etc.
You can try to invest and increase your earnings. There also are ways without investing to increase earnings.
Like games or getting referrals. The referral program is really nice.