As an aside, many grammar books highlight these words as frequently misused.
* lie, lied, lied: (say a false thing) - He lied to me. Have you ever lied to your mother?
* lie, lay, lain: (vi - to be in horizontal position, to be at rest) - Happy days lay ahead. He has lain in his bed for a week.
* lay, laid, laid: (vt - to put something in a lying position, to place) - He laid himself down. The groundwork was laid.