First, the online market is different from the print market.
However, like the print market, you should first determine your audience.
Who are you writing for?
Are you writing for an online children's market? Are you writing for online business professionals? Are you writing for those seeking information on shopping, on education?
What type of writing are you doing? Creative writing? Business articles? General web content?
What market are you writing for? Blog? Web content provider? E-book?
These are the questions you should first ask yourself before you begin writing.
Most online writing is conversational, directed at the market that you're writing for.
Many of the paragraphs are shorter than paragraphs in the traditional market. Most make use of keywords. For example, let's say the keywords in this article are "writing" and "market" then "writing" and "market" should be in most of the paragraphs.
When people go to the search engines to search for articles on "writing" and "market" as in literary markets, then it's likely they'll find this article and/or other articles that make use of these keywords.
You should also try to find markets where you can consistently publish and sell your online writings, whether it's shvoong, Associated Content, Constant Content, Triond, and/or other online markets.
You should write consistently and try to publish consistently.
You should read and best of the online writings and learn from the best online writers.
You should edit and proofread your online writings.
You should keep an idea notebook of ideas and titles for online writings.
You should keep a research notebook to do up-to-date research on the various articles and ideas for articles.
You should continue to read, write, and learn about online writing and you should continue to research online literary markets.