You don’t have to become an English professor to write a good memoir, but certainly some knowledge of grammar can’t hurt so that you avoid common slip-ups. The lie/lay confusion represents one of the most frequently made errors.
When people or things do the action on their own, use the word lie or, as a participle, lying: the cat just lies there in the sun; the book is lying on the table; the girl likes to lie on the sofa; I was lying on the beach one day. When someone or something causes the action to occur, use the word lay or the participle laying: she should lay down the law; I am laying the book on the table; he always lays a mat on the floor to keep people from tracking in mud.
The error on this is that people tend to use lay when they should use lie. The error rarely goes the reverse way. Once you get accustomed to using both words correctly, the usage will come easy to you. Part of the problem is that lay is used so often that the correct word lie doesn’t sound right to most people even when it is. These two words cause even more confusion in the past tense, which I’ll talk about next time. Now go back to writing your memoirs!