I don't believe in finding a 'best way' to improving your tech writing skills. But what I can recommend is that researching and writing several technical blog-posts on certain interests that you think could be useful for others are very good ways in knowing how to communicate with a technical audience and improving your tech writing skills. This is done on HN every day.

Also get someone else to look at your report/blog/white-paper/etc for proof-reading as you might not be able to see your own mistakes as you write it.

Lastly, reading and quoting the references are always a must. Also a way of improving your technical knowledge and writing too.