Lie, Lady, Lie

We're taking a break from punctuation this week to look at the difference between "lie" and "lay."
Have you looks at my Parts of Speech page? One important part of speech - well, they all are really - is the verb. Verbs can be transitive or intransitive and all that means is that the transitive ones take an object. That sounds rather abstract so here are some examples:
"I live in a house" vs. "I love my house." In the second example "my house" is the object of the verb "love." So love is a transitive verb. You need to love something. "Live" is intransitive, i.e. it has no object. You can live your life, in which case the verb has become transitive because "life" is the object.
Many verbs can be both. You can sing a song or sing beautifully. But some are resolutely intransitive, like "sleep." But you can say "I slept a long sleep," even though it isn't very idiomatic.
How does this help with "lie" and "lay"? Well, "lie" is intransitive; it doesn't have an object. Whereas "lay" requires an object:
"I always lay the table half an hour before a meal."
"Our best hen lays an egg every day."
but
"If I lie down on my bed after lunch, I always fall asleep."
The confusion arises because the past tense of "lie" is "lay."