Write in active voice. That's the single most important lesson I learnt when writing technical specifications.

The #1 goal of technical writing is to be clear and accurate, so passive voice should take a back seat unless you cannot phrase it otherwise. Active voice lets you convey clearer, more concise statements that describe a concept.

Take for example "the ball was thrown by the man" vs "the man threw the ball". The latter is much more concise and easier to parse because the active object preceeds the passive one and so the concept unfolds linearly.

If you're using Word for writing, go into options > proofing > find 'writing style' and hit 'settings' > turn on 'passive sentences'. I just throw it to the default 'grammar & style' because I'd prefer to know of and actively decide against style issues than not. It's helped drill my writing significantly.

I am no expert, but a few things that helped me:

1. Read lots.

2. 30 Days to a More Powerful Vocabulary by Norman Lewis. Some the words I have inly encountered once or twice in the intervening 25 years since I read it, but many others I hear every day.

3. The Elements of Style by Strunk and White. It’s like any other instruction manual. It’s worth reading, even if you don’t follow them.

I found this book to be a wonderful resource on tech writing: https://www.macmillanlearning.com/college/us/product/Technic.... You can sometimes find a cheap used copy. The material hasn’t really changed all that much between editions.