[eldacila]

I'd say focus on making things clear and simple. Use period (.) more often, use less commas. Also write first, then edit for clarity. But don't re-write from scratch. The Easy Approach to Requirements Syntax attempts to fix some problems with "normal" system requirements (and they used those for automotive and I think aviation systems, so if they made progress, you know it's real), give it a read (focusing on the problems they are trying to solve, and see if that applies to your writing)

several people say to avoid passive voice (I'd agree, but don't believe me, see some examples of this)