Usage Tip: Lie vs. Lay

When you're dealing with the present tense, it's pretty simple to keep it straight. "Lay" is a transitive verb -- you lay something, meaning you put it down. A direct object is required (direct objects are boldfaced):

I lay my head on my pillow.
She lays her hands on his head.
They lay their magic carpets in the garage.

"Lie" is an intransitive verb, meaning there's no direct object required. It's something you can do all by your self:

The dog lies in the sun.
I am lying on my belly.
The oysters lie on the beach.

Use this as a memory device for lie vs. lay in the present tense: You lay something down, but people lie down by themselves.

I shall let Grammar Girl explain the usage tip for past tense:

...But then everything goes all haywire, because lay is the past tense of lie. It's a total nightmare! I tried and tried to come up with a mnemonic for this, but I couldn't do it. Instead, I've made a table that you can print out from the website and tape up over your desk or in your notebook, because you just have to memorize this or look it up every time. [see graphic above]

So, anyway, here's how to conjugate these two verbs:

The past tense of lie is lay, so:

Last week, Steve lay down on the floor.
The cat lay in the mud after it rained yesterday.

The past tense of lay is laid, so

Last week, I laid the TPS report on your desk.
Mary forcefully laid her ring on the table.

The past participle of lie is lain, so

Steve has lain on the floor for days.
The cat has lain in the mud for hours.

The past participle of lay is laid, so

I have laid the data sheet on your desk.
Mary has forcefully laid her ring on the table.