Once you start writing, make sure you have the list of the keywords you want to use, next to your PC. Don't have them on your screen—print them out or write them down. This is because you need to be able to write the content of your page without having to switch back and forth from one application to another to view the list. Get those keywords into your head and start writing your article. You will see how it will flow into your content without much effort.
One thing that I always struggle with is the structure of my content. By structure I mean the way in which content is placed on the page, does it have a natural flow, or is it jumping around and changing focus all the time. It is important for your visitors to have some sense regarding where the article is heading and how it can help them.
I learned a nice trick that you too can use:
Write the most important subject of your topic first
Add the sub-topics below the main ones...