Leave it lay
When I first began teaching editing a Loyola College in Baltimore (now Loyola University), I was straightforward about grammar and usage, after the manner of nearly all the textbooks on copy editing: These are the standard errors, the common misuses, the common confusions; mark them and sin no more. You have the Law and the Prophets; what more do you need?
Over time I have developed a more nuanced approach, and now my handouts and godly admonitions identify common errors, misuses, and confusions, but also superstitions to abandon, and points of grammar and usage that are in transition. There are distinctions, I tell my undergraduates, that you should maintain only in the most formal contexts or for the fussiest audiences, and that you might as well ignore elsewhere.
Anatoly Liberman, writing at the Oxford University Press OUPblog, gets at the issue:
Discussing lie and lay for the umpteenth time would be even less productive than beating ~ flogging a dead horse. In some areas, the distinction has been lost, and so be it. English has lost so many words in the course of its history that the disappearance of one more will change nothing. So lay back and relax. The same holds for dived/dove, sneaked/snuck, and the rest. I only resent the idea that some tyrants wielding power make freedom loving people distinguish between lie and lay. Editors and teachers should be conservative in their language tastes. In works of fiction, characters are supposed to speak the way they do in real life, but in other situations it may be prudent to lag behind the latest trend as long as several variants coexist.
I feel obliged every semester to go over lie and lay, but the blunt fact is that nearly all my students are just baffled. They do not hear a distinction; they do not encounter it in speech or in much of the writing they encounter. I might as well be standing at the blackboard telling them that they will be graded on how well they grasp the middle voice in Greek.
I would much prefer to tell them that the lie/lay distinction with which their grandparents were tormented in school is over, and that, moreover, everyone/they has finally carried the day and we can all go on to discuss more interesting points of usage. But out there, still, I sense lurking the readers bringing down a metal-edged ruler on the knuckles or reaching for a rattan cane to administer six of the best.
I have only so much time with them in a semester, and I have to counteract the bad teaching about language that most of them have had, to indicate the points that matter most to literate readers, and to show them how to gauge how the levels vary by audience, publication, and occasion. So, you viewers-with-alarm and we-need-an-English-Academy peevers and when-I-was-a-boy harumphers out there, how about giving it a rest?