You can't really say that a certain field is the best way. I know many people that are very successful online. One thing they all have in common: they have a passion for what they do, and the service or product they provide. If you want to make money online, find someone you are passionate about, and build a business around it with lots of market research.
Yes I am earning right now. I am earning by article writing and cartoon making. My earning amount is $500 per month.
I Make around $3500 a month creating mobile websites for local businesses. http://www.mobileinternetbiz.com
Look around the internet. I would say 99% of sites have some kind of monetazation (even if they're not successful). Each time you are on a web page look around and try to find out how they make money.
So many people are making LOADS of money online.. Just find the niche that works for you. Be creative and actually ADD something to the internet. If people see value in your services / site / product then it will promote itself
There are many ways to earn online,Blogs,Article writing,Google Adsense,Manny download site.All you can search at google.