There are many models you can earn money from online blogging, there are platforms such as Hubpages that offer you some commission from writing and ranking a good post. However you use their property to do so.
You might start write some blog on your preferred niche, you shouldn't write randomly as it becomes more difficult to luckily rank in some long tail keywords without any research at this time.
To sum up
1.) Pick your niche, brandable domain, and hosting offer.
2.) Start keyword research you should give 50% of your attention here 30 for writing and 20 for revision.
3.) Optimize your article both on-page and off-page for your researched keyword, every article, post, category should have their own purpose and be able to rank in its potential keywords.
4.) Communicate with other websites in your industry, get visibility on social media, create your small followers.
5.) Now you can think of the way to monetize, will it be ads revenue, commissioned base affiliate site, or sell your own product?
If you have any question just drop it here and i can come back and answer it for you.