Once you've written the text of your HOWTO, it is time to polish and refine it. Good editing can make the difference between a good HOWTO and a great one.
One of the goals of editing is to remove extraneous material that has crept its way into your document. You should go through your HOWTO carefully, and ruthlessly delete anything that doesn't contribute to the reader's understanding of the subject matter. It is natural for writers to go off on tangents while in the process of writing. This is the time to correct that.
When editing and proofing your work, you must check for obvious mistakes, such as spelling errors and typos. However, you should check for deeper, but less obvious errors as well, such as "holes" in the information. Make sure that the contents of every section match the title of that section precisely.
When you are completely satisfied with the quality and accuracy of your work, forward it to someone else for third-party proofing. You will be too close to the work to see fundamental flaws.
In a sense, editing is like code review in software development. Having a programmer review their own code doesn't make much sense, does it? Why should having a writer edit their own document make any more sense? So, recruit a friend, or write the ldp-discuss list to find a volunteer to proofread before submitting your HOWTO.
If you are writing in a language in which you are not fluent, I strongly recommend that you seek an editor who is. Technical documentation, more than any other type of writing, must use extremely precise grammar and vocabulary. Misuse of the language, no matter how understandable and unintended, makes your HOWTO less valuable.