Writing tips from the EC editors
This is the most common verb tense error.
From Dictionary of Problem Words and Expressions by Harry Shaw:
'Lay' means "to place" and is a transitive verb requiring an object.
Present tense (lay): Is it better to lay a baby on its stomach or on its back?
Past tense (laid): She laid the baby gently in the crib.
Past participle (laid): She had laid the baby there dozens of times before.
'Lie' means "to recline", is intransitive, and takes no object.
Present tense (lie): My dog loves to lie on my bed.
Past tense (lay): The man lay where he fell in the street.
Past participles (lain): He has lain there all night.