Object-of-verb pronouns:
Direct object:
me nos
te os
lo, la los, las
(Le as a direct object: In some parts of Spain, le can substitute for lo as a direct object when it means "him" but not "it." Less commonly in some areas, les can substitute for los when referring to people.)
Indirect object
me nos
te os
le (se) les (se)
(Se as an indirect object: When there are two third-person object pronouns, se is used as the indirect object form.)
Reflexive object:
me nos
te os
se se
Order of object pronouns: When you have two object-of-verb pronouns, the indirect will
precede the direct and reflexive will go before either of the other two. In other words, the order is Reflexive
/ Indirect / Direct, or RID.
Indirect before Direct, Reflexive first of all.
Placement of object pronouns (direct, indirect, reflexive). The object pronouns are placed:
(1) immediately BEFORE a conjugated verb Yo como el bistec. Yo lo como.
(2) immediately BEFORE the verb of a NEGATIVE COMMAND No lo comas todo.
(3) AFTER AND ATTACHED to an infinitive. Voy a comer el bistec. Voy a comerlo.*
(4) AFTER AND ATTACHED to a present participle (gerundio) Estoy comiendo el bistec. Estoy comiéndolo.**
(5) AFTER AND ATTACHED to an affirmative command. Come el bistec. Cómelo.
The above rules are rigid except that in cases where you have an infinitive dependent on a conjugated verb* and a present participle dependent on a conjugated verb**, you may put the pronoun BEFORE the conjugated verb* or following and attached to the infinitive or gerundio.**
*Lo voy a comer.
**Lo estoy comiendo.
Generally, the indirect object pronoun is used in addition to the noun indirect object. In other words, we have the following possibilities:
María me da el
libro. María me lo da.
Maria gives me the book. Maria gives it to me.
Yo le doy el libro a María. Yo se lo doy (a ella).
I give the book to Maria. I give it to her.
A good "general" rule: when you have an indirect object, always use the indirect object pronoun EVEN when you also name the indirect object noun.