1. In a sentence that requires a direct and an indirect object pronoun, the INDIRECT OBJECT PROJECT is written FIRST then the direct object pronoun follows.
E.g.: Me cantó la canción becomes Me la cantó which means: He/She sand me the song.
2. In the case of an infinitive both the direct and the indirect object pronouns may be added to the end of the verb BUT AN ACCENT is REQUIRED above the vowel in the final syllable of the verb in the infinitive.
E.g.: Decidí escribir la información a ti becomes Decidí escribírtela which means: I decided to write you the information.
3. Object pronouns precede verbs and affirmative and negative words precede object pronouns.
E.g.: No me lo dieron. – They didn’t give it to me.
4. In a sentence which both the indirect (le or les) and direct (lo, la, los, las) object pronouns are required to be in the third person, the indirect object pronoun is replaced by “se”. That is, “le” and “les” become “se” before “lo”, “la”, “los” and “las”.
E.g. Se lo describí a ella. – I will describe it to her.
¿La silla? Se la vendemos al señor. – The chair? We sold it to the gentleman.
5. For emphasis or clarification, prepositional phrases such as a él, a usted, a ella, a mí etc are used with indirect object pronouns.
E.g. A mí me gusta mucho tocar el violín. – I like to play the violin a lot.
¿A ti te dieron eso? – They gave you that?
Ya se lo mandé a usted – I already sent it to you sir.