DIRECT OBJECT PRONOUNS:
me, te, nos, lo, la, los, las
We use ME when Yo (yourself) is speaking.
We use TE when we are talking to Tu (you.)
We use NOS when we are talking about Nosotros (us.)
We use LO when we are taking about El, Ella and Usted (he, she and you-formal.)
We use LOS when we are talking about ellos, ellas and ustedes (them and you all.)
INDIRECT OBJECT PRONOUNS: me, te, le, nos, les
We use ME when implying: me, to me, or for me.
We use TE when implying: you, to you, for you.
We use LE when implying: him/her, to him/her, for him/her or you-formal, to you-formal or for you-formal.
We use NOS used when implying: us, to us, for us.
We use LES used when implying: them, to them, for them, you all, to you all, for you all.
When direct and indirect object pronouns are together in a sentence, the indirect object will be placed before the direct object pronoun.
Me la trajo. = He brought it to me. (La cuenta)
Te lo trajo. = He brought it to you. (El plato)
Nos las trajo = He brought it to us. (Las bebidas)
The indirect object pronouns LE and LES both change to SE when followed by the direct object pronouns lo, la, los or las:
Se lo trajo. = He brought it to him/her. (El postre)
Se la trajo. = He brought it to him/her. (La servilleta)
Se los trajo. =*He brought them to them. (Los menus)
Se las trajo. =*He brought them to them. (Las bebidas)
* The first THEM refers to the objects he brought since LOS and LAS is in plural form. The second refers to the pronoun ELLOS.