How does one improve their technical/scientific writing?

There should be a number of ways to do this:

• read, everything,
• be curious about all topics of interest, it will develop your vocabulary,
• have a co-worker/ trusted professional review your work and critique it,
• ask for feedback from customers (your audience),
• be a grammar nerd, follow and participate in on-line discussions,
• take a look at your old work and see how to improve it,
• join, or form, a group of like minded people and review each others' work, present to one another topics of interest that you've researched.  You can even give the group an exotic name and yourself a lofty title.