The Proper Use of “Lay” and Lie”

I received an email from a reader asking me to clarify the usage of “Lay” versus “Lie”.  For some reason people have trouble with these two pesky words. In truth it is simple to keep them straight if you remember one rule.  We will get to that later.
The main difference between the two words is that lay is a transitive verb, while lie is an intransitive verb. Now, I know that those may seem to be big words, but let’s break them down just a bit. A transitive verb is one that takes action on an object (Example: Please lay the book on the table). However, an intransitive verb is the complete opposite and therefore does not take a direct action on an object (Example: Why don’t you lie down?).
The only reason these verbs present a problem for anyone is that the past tense of the verb “lie” is identical in appearance to the present tense of the verb “lay.”  Now it is time for some English 101.  Every verb has three parts:  Infinitive, Past Tense and Past Participle.  Let’s take a look at a table that shows how our two combatants shake out:

Verb	Infinitive	Past Tense	Past Participle
Lie	Lie	Lay	Lain
Lay	Lay	Laid	Laid

Now, I will admit that it is easy to get confused after looking at the table.  So, let’s get to that simple rule I promised to help solve your dilemma.  So here’s the how to do it:

1. Today you need to lie down.  Yesterday you lay down.  In the past you have lain down.
2. Today, you lay the book on the table. Yesterday, you laid the book on the table. In the past, you have laid the book on the table.

I hope this helps you figure out these two words.  I don’t know why people are so picky about them.  I can’t count how many times I have been corrected on their usage.  Does it really matter if I lie on the floor or lay on it?  Do you know what I mean?