Make it scannable. Create an outline before you start. Type the main points as you think of them. When you're done, organize them into steps. Use bullets, numbers, etc. to make them stand out, then fill in the details. Readers should be able to get an idea of your tutorial with just one look.
Use proper grammar and punctuation. You don't have to be an English professor. Just use complete sentences, capitalize only when necessary, don't mix up your periods and commas, and so on. Your goal is to make your how-to as easy to read as possible.
Begin with an introductory paragraph. Introduce your how-to by telling your readers what they'll be learning. You can also tell them why you've written the article and what kind of expierience you have. Don't try to squeeze in too much information. The focus should be on the knowledge you're providing.
Remember your beginnings. Think back to when you first began learning about your topic. Things that seem obvious now were a mystery then. If you could go back in time, what would you tell yourself to make things easier? This is the same advice that will help your readers.
Tell them how, not about. Many of the tutorials we see are written without real instructions. For example, rather than saying, "Shoot them in the fucking head.", they might say, "Aim at their head, and fire" Don't confuse your readers. Clearly show the steps that they need to do.
Keep your paragraphs small. Research has shown that the average reader learns best when paragraphs are 3-5 sentences long. So basically most people have attention spans of a nut. (This includes me). This helps them to digest each idea before they move on to the next one. It also helps you maintain enough white space.
Use white space. The use of whitespace makes it look easier to read. Leave a couple of blank lines between sections. Look at the finished instruction as a distance and ask , "Does it look too cramped up?". Especially when a topic is difficult, a big mass of words can scare your readers away
Try for variety. Your how-to may be about cats, but there's only so many times you can use the word "cat" before you bore your readers. First, ask yourself if a word really needs to be in the sentence. Second, consider similes; for example, "kitty", "feline", "furry friend" and so on.
Use simple language. The average adult reads at an eighth grade level. To be able for your reader to be understood, write in the clearest, simplest manner possible. For example, the word "copy" is better than the word "replicate".
Use acronyms sparingly. Acronyms can be useful, but overusing them will cost you readers.
No-one wants to wade through a sentence like this: "Your SDRAM/DDRAM will depend on your MB, CPu and OS."
Some things are better spelled out: "The type of memory you'll need (SDRAM or DDRAM) will depend on the requirements of your motherboard, CPu and operating system."
Stay positive. Replace negatives with positives wherever possible. Some examples:
"Don't smudge your work." is replaced with "Rest your hand on a piece of paper to avoid smudging."
"Only the uncivilized gulp their wine." is replaced with "Sip your wine slowly to fully appreciate its flavor."
I hope this tutorial will be helpful to any one who wish to write a how to article.