Indirect Object Pronouns

Indirect Objects: Indirect objects indicate where the direct object is going.
It indicates TO WHOM, FOR WHOM, FOR WHAT, TO WHAT?

He gives the book to María.
Where is the book going?
To María. IO=María

Diego me compra un regalo
Diego buys (for) me a gift. IO=Me

*Le and Les are meant to be ambiguous, so they can stand for different thigns

Ella le escribe una carta.
(when given this sentence, it can mean any of the following):
She writes him a letter.
She writes her a letter.
She writes you (formal) a letter.

Indirect Object Pronouns:

me (me)
te (you)
le (him, her, you)
nos (us)
les (them, you all)

Place the pronoun before the conjugated verb. Easy as that!