Making progress on grammar

I’m enjoying the online course that I’m taking (Grammar, Mechanics, and Usage for Editors).  The assignments are quite challenging, particularly those that involve identifying different sentence types or parts of sentences. I’m still struggling with the difference between phrases and clauses, and between simple, compound and complex sentences. However, the course notes are helpful, and the main text for the course – A Writer’s Reference, by Hacker and Sommers – has lots of useful practice exercises.