I've been providing written content on the Warrior Forum full-time for over a year now and thought that I'd share some tips that I use in my business.
These suggestions assume that you have already researched your topic and are ready to write your article.
1. Focus on Completing the First Draft.
I have found that my efficiency is higher when I try and complete the first draft of the article quickly. I try not to recheck what I have written or even correct spelling errors until the 1st draft is complete. This allows me to get all of my ideas down quickly and helps reduce procrastination. After I have the draft ready I can then go back and edit it to make sure that the key points have been presented optimally.
2. Eliminate Distractions
Eliminating distractions complements the first suggestion. I use systems to ensure that I am focussed on the task of writing. I use the free app OmmWriter and have fallen in love with it. It's a text editor that goes full screen blocking out all distractions. Additionally it plays calming music and has a serene backdrop. Very Zen, and highly recomended: Welcome - Ommwriter
SelfControl (An app for Mac users) has rocked my world. It blocks internet access to specific sites (or only allows you access to your 'whitelist') for a chosen period of time. The best part is that once you start the app it can't be stopped until the timer expires (even if you uninstall the software or restart your computer). Pretty full on, but amazing for productivity. Download SelfControl for Mac - Block distracting websites for predetermined periods of time. MacUpdate.com
Other than listening to the music of OmmWriter I sometimes listen to whitenoise or nature sounds (there's a great free iPhone app called White Noise or you can check out RainyMood.com: Rain makes everything better.). I often listen to Hindi music too which I find less distracting than songs that feature English lyrics.
3. Write Early in the Morning
This tip will not apply to everyone equally...some people work more effectively in the morning while others have better results at night.
I choose to write in the morning (often it's the first thing I do after making a cup of tea) because I find it easier to complete the writing process from start to finish than I do later in the day.
Additionally, if I leave articles to complete until later in the day they can seem more and more overwhelming, which leads to procrastination.
4. Adjust as Your Energy Drops/Increases
Writing articles can be draining, I think Jason Fladlien once equated it to slave labor.
In the mornings I typically can write full articles without needing breaks, but come afternoon this idea becomes overwhelming and it can be hard to focus on an article from start to finish without taking a break.
So when my energy drops I typically work in 5 minute bursts with a 1 minute break in between. Here's an interval timer I use: Interval Timer - Online Stopwatch
I also break up the articles into sections and use a countdown timer on my iPhone to time each one. When I complete a section I rest until the time runs out and then I start the next part.
5. Consider Using Speech-to-Text Software
I go through phases...sometimes I am more efficient using such software and sometimes I get more written by typing.
The important thing to realize is that you probably dictate differently to how you type. For example, my language sounds more formal when I type than when I dictate (depending on your audience, writing in a formal style is not necessarily a good thing).
Keep in mind that using software usually requires extra editing time to correct mistakes. If you need a free alternative there is a Dragon Dictation iPhone app. It's not completely accurate and can only record in 1 minute bursts. When I have used it I dictated the article into my phone and then emailed it to myself so that I could edit it on my computer.