From The New Yorker comes "The Comma Queen" video series, which features Mary Norris talking about the finer points of language that come up again and again in our everyday writing. Some of it, no doubt, will come in handy.
Norris began working at The New Yorker in 1978, and has served as a copy editor/proofreader for much of that time. Suffice it to say, she can tell you some instructive things about language.
Above, we start you off with Norris explaining the difference "who" and "whom," and then "lay" and "lie." (Bob Dylan take note.) This other clip -- focusing on "less" v. "fewer" -- gets into a pet peeve of mine. By the way, did I use those dashes correctly in the previous sentence? Well, there's a video about that too.
And it's worth noting that Norris has a new book out called Between You and Me: Confessions of a Comma Queen.