Do you have an outline? If you do, cover your outline, then expand, then edit, edit edit. rearrange, cut, add, etc. If you don't have an outline? get an outline, dawg. I have wasted SO MUCH TIME writing articles without outlines and now I am a convert. I find them so much easier to organize my thoughts and get from A to z.
First thing I ever write is my "Table of Contents" ie. logic flow ie. outline. It helps to know where you think you are going. Even if that changes along the way and you have to modify, if you fail to plan, you plan to fail.
Unfortunately, I'm pretty new to writing (outside of simple highschool and college essay stuff), and haven't taken any real classes on writing, so I'm not too used to using outlines and forget to 99% of the time. I need to make one and flesh it out, because it's getting hard to reread everything a lot to see what I've covered already. Thanks!
only other tip: Don't worry about how things are going down on paper the first time, and don't be precious about your words. If you're really passionate about your subject and you want to get it right, you'll be writing 90% of it over again (or more, ask KB about his book). Last thing. Someone once said to me, "don't focus on being perfect, because you will never be perfect". I find this a very freeing concept: it gives you permission to make mistakes to take risks. I do my best to embrace it. There's lots of great writers here, hopefully they can hook you up with further good advice.