It seems to me that when people have conquered the two/too/to fiasco, or the there/their/they’re conundrum, they give up, convinced of their mastery of the English language. And I know I’m probably going to sound  kind of like an  asshole for saying this, but I’m just going to say it anyway, because I know when to use “lie” and when to use “lay” in a sentence, and that gives me an undue sense of entitlement, which I plan to milk for at least the next three paragraphs.
It’s crazy the number of submissions I read that have lie/lay mixups in them. Some of them are really great stories, too. And then I stumble over a  I want you to lay down. Okay, I’ll say this, and you can write it on a post-it note: you  lay something on the table, and you  lie down on the couch. Is it a pen? Are you putting it somewhere? You  lay it.  Lay requires a direct object (the pen).  Is it your body? Are you throwing it into that hot bartender’s bed? You  lie down. You lie down sexily.
The past tense is a little trickier, because the past tense of  lie is  lay. (Last Wednesday, we lay down in the grass.) The past tense of  lay is  laid. (Henry laid the fork down instead of stabbing Julie.) You can put that on the post-it note, too. It’s not really cheating.
Yes, this means that the Snow Patrol song “Chasing Cars” is grammatically incorrect. Sad as it is, it can’t be undone. But you now hold the key to constructing proper sentences using lay and lie. And we all know there’s nothing sexier than proper grammar.