The document level? meaning chapters and such? This has more to do with your understanding of the material, and less to do with the act of writing. You should have, in order, a title (along with date, author, etc), table of contents, abstract and definition of terms in the case of technical documents, a introductory chapter/part, the contents, a conclusion chapter/part and a bibliography in the case of technical documents.
As for the other two categories:
Each time you want to write analogies write a metaphor instead — at most 5 words, and make sure it doesn't require explanation (it's a bad metaphor otherwise). Analogies are long and boring. When you mean to write a analogy, a lot of the time what you really intend is a metaphor.
Don't explain yourself. What I mean is having follow up sentences like this one explaining what should have been "understood" in your sentences. It's better to write it out clearly: "don't write about what you're currently writing" or "avoid meta-writing." Eliminate the follow-up or the initial sentence to fix the problem when it appears (whichever one robs the other of it's thunder).
Don't start a sentence with "However," "But," and so on; you can do so occasionally if it's for emphasis. I recommend using a semi-colon to link the two sentences together when they are related (like I have done in the previous sentence) or parentheses for a short note. Em dashes can also be used, but sparingly. If the sentence is not related, just simply start with the subject. You can also scrap the sentence altogether and rephrase it as a different kind of sentence, such as a rhetorical question opening the way to some new chain of thought.
Avoid "pleonasms" (redundant or repeated terms). It doesn't have to happen in the same sentence; if you emphasize something in one sentence try not emphasize it again (just in a different way) in your next sentences. No need to beat on a dead horse.
However that's not to say true pleonasms aren't something you should worry about: 12 midnight => midnight, 12 noon => noon; 3 am in the morning => 3 am; biography of her life => biography; each and every => each; end result => result; personal opinion => opinion; personally, I think/feel => I think/feel; cooperate together => cooperate; etc etc.
Any word, expression or sentence that doesn't add anything or change the sentence is just fluff, and you should omit it. Reduce clauses to phrases, phrases to single words. Remove intensifiers that don't intensify. Avoid words such as really, very, quite, extremely, severely (intensifiers). And more importantly, use your own words. Using "fancy wording" just results in writing clichés, which makes your writing dull. (more info and examples) So when is it okay to use a cliché construct? When it's a saying or otherwise a very popular, and well understood, metaphor.
You can find simple exercises on the net.