I have been doing two things lately: editing my own book and reading student work. I don't know which is more frustrating. With my own text at least I know what I want to say. With students' texts, I usually know what they want to say, but good pedagogy is to make them realise what they want to say and then let them say it.
I am a vicious supervisor. I learned it from my own professor many years ago. She made me shed many tears, but her editing was brilliant. I make students delete sentences that repeat the previous sentence with a slightly different wording. I make them delete all “In my opinion” (because everything not referenced is supposed to be their opinion), all “It would be interesting to consider” (because it is an empty phrase), all pairs of synonyms (“problems and issues”), all “as such”, “moreover”, “indeed” and “in fact”. Then I start editing my own text, and all these faults come over me in a deluge (except “in my opinion” - I learned to avoid it when I was a postdoc).
The best training in succinct academic writing has for me been writing for encyclopedias. If you have five hundred words for an entry you have to be economic with words. You need to squeeze tons of information in these few words, so each word must be chosen carefully. You don't want to waste your precious word count on “moreover” and “in fact”. I admit that occasionally such small words can be useful, but mostly they are garbage. It's incredible how much better a text becomes when you prune it from 735 words to 499. When you have learned that, cutting from 7,000 to 5,000 is child's play. Writing encyclopedic entries should be mandatory in doctoral training.
It is illuminating to look at your own text after having read other people's theses. Reading theses, I wear my evil assessor's eyeglasses and notice all the minuscule repetitions, inconsistencies and circular arguments. I need to be like that toward myself.
Guess how much I have pruned this post.