The verb to lie means to rest or recline and is conjugated lie, lay, have/has lain. He lies silently in his bed. Yesterday, I lay on the beach. The dog has lain on the couch many times.
The verb to lay means to put or to place and is conjugated lay, laid, have/has laid. We lay the books on the desk when we’re finished reading. He laid the baby in the crib yesterday. He has laid the keys on the table every day this week.
In order to avoid this grammar error, just remember that when you use the verb to lay, there should be an object after it—the thing that you are laying (putting or placing).
Sherry
Sherry’s Grammar List and Paul’s book–Literally, the Best Language Book Ever
Everything Language and Grammar 
I always forget to use “have/has lain” instead of “have/has laid.” Maybe this time I’ll remember it. 🙂