In high school, I was lucky to have multiple teachers who were sticklers for imparting the essential building blocks of strong writing. We spent a lot of time "in the weeds," rote-learning vocabulary, sentence patterns, paragraph construction, and finally, structures for the expository essay (above and beyond the academic essay we mastered in school.)

The surprising thing, even to someone like me who considers herself a good writer to begin with, was how important working through each "level" of writing was. While I haven't reviewed the foundations in a long time (I probably should), because I spent so much time painstakingly memorizing the contents of each earlier on, I can now write quickly and confidently and usually be pretty close to correct.

Here are some books I'd recommend for each level:

1) Vocabulary - Wordly Wise (the older the version of the book, the better the word lists), such as here: http://www.amazon.com/Wordly-Wise-Book-Kenneth-Hodkinson/dp/...

2) Sentence structure - The Art of Styling Sentences, http://www.amazon.com/The-Styling-Sentences-K-D-Sullivan/dp/...

3) Paragraph construction - Paragraphs and Essays (the part on paragraph construction and patterns is very straightforward, basic, and clear, I don't think it's worth buying the whole book though), http://www.amazon.com/Paragraphs-Essays-With-Integrated-Read...

4) Expository essays - Encounters: Essays for Exploration and Inquiry (this is the textbook NYU uses to teach "Writing the Essay"), http://www.amazon.com/Encounters-Exploration-Inquiry-Pat-Hoy...