For most online writers looking to earn an income, Google Adsense is their best friend. Of course, some writers use Amazon, Chikita or Affiliate Sales programs because it gives them a little bit more income, but if you read the monthly earning reports here, you will see that most writers get the meat of their income from Google Adsense. So logically, one important aspect of increasing your income on not just Infobarrel but any other content you have is optimizing your Adsense through placement and keyword selection.
On Infobarrel writers have no way of changing the placement of their Adsense ads (to my knowledge, please correct me if I'm wrong), so this does not directly apply to us. However, anyone with their own private blog can manipulate the placement of their Adsense ads to increase their click-through-rate. I cannot give specifics as I don't have any non-Infobarrel content, but manipulating the placement of ads can increase or lower their return. There should not be too many ads as this will discourage potential readers, yet they should not be so skimpy as to make them invisible to the reader.
For us Infobarrel writers, we can have a direct impact on how much we earn from our ads through our writing. Essentially, it is our content that will help search engines drive people to our articles, as well as ensure high-paying ads that people are interested in clicking on are placed beside our articles. Many people speak about "keyword density", i.e. the amount of times you repeat your chosen keyword in your article. Various sources on the internet put the optimal amount from anywhere between once every 50 words to once every two hundred. Keep in mind your keyword will have a big impact on your search engine ranking and the ads being shown beside your content.
The rule of thumb I use is to write my article first in a smooth and flowing way, in order to keep it as natural and easy to read as possible. After that, I go through it and count how many times I used my keyword, and make changes accordingly. If I can add more keywords without fundamentally altering my article, I do it. But if I see that I will just turn my article to spam if I cram in my keyword a few more times, then I won't increase its count.
Everyone has a different style of writing. Personally, I write when I'm inspired, or in the "zone". Basically I don't do much planning and Search Engine Optimization (SEO) because I prefer to write first, and count the dollars after.