Here are some random things I've learned while writing technical documentation:

• When talking about concepts, using singulars makes for clearer reading than using multiples. For example, rather than composing a sentence like this:

  "Applications built with foobar may be frobnobbed using fleebars."

  It's usually clearer to say something like:

  "An application built using a foobar can be frobnbbed using a fleebar."

  Personally, I find keeping to the singular keeps things concrete, and prevents the text from careening into the abstract too quickly.

• Don't be afraid to repeat yourself. Use pronouns sparingly. For example, it's often clearer to say: "The cat sleeps on the sofa. The cat is a tommy" rather than "The cat sleeps on the sofa. It is a tommy." Is the cat or the the sofa a tommy? The first form is repetitive, but it's crystal clear that the cat is a tommy.
• Examples beat any amount of purely narrative explanation.