Give the reader a general idea of what the project entails before beginning. Provide a list of tools and materials that the reader will need for the task. Use succinct captions underneath photographs. Remember, clarity is of the utmost importance. Be aware of unstated assumptions on your part. For instance, one writer was explaining how to press flowers.
"Turn the book sideways and start by placing the flowers in rows, with the stems pointing towards the outside edge. Gently close the book and place a heavy object on top. A couple of bricks will do. It will take up to two weeks for the pressing to be done."
If you followed the writer's advice, you would have to lug bricks to the field and then wait two weeks until the flowers were pressed. That's where the editing comes in.
Put yourself physically in the picture. Include appropriate warning when explaining instructions. Define unfamiliar terms and use adjectives and adverbs sparingly. Sometimes words are not enough: include a diagram or photo when appropriate.
Inject some humour into your article. One writer who penned a piece for Single Parent Family magazine about the tedious task of clearing your house of clutter, titled her piece "Showdown at the OK Corral", complete with cowboys and tumbleweed. If you do frame your article around a metaphor, make sure you return to it at the end to tie the piece up nicely.
For more information, visit http://www.wikihow.com/Write-a-How-To-Article.