The Imperative in Pronominal Form
In the affirmative imperative, the pronoun markers are always placed at the end of the verb. We say that there is enclisis of the pronoun:
despertarse (to wake up) => despiértate (wake up)
However, there are some spelling modifications to anticipate. First of all, the final -s of the first person plural disappears for reasons of sound:
despertarse (to wake up) => despertémonos (let's wake up)
Then, in the second person plural, it is the turn of the final -d to disappear with one notable exception for the verb ir (to go), since it only has two letters (id), we keep the final -d in its case. But it is the only exception.
despertarse (to wake up) => despertaos (wake up)
irse (to go away) => idos (go away)
Note that these spelling modifications only occur for pronominal verbs. When it is another pronoun, there is no longer this type of modification.
les separar (to separate them) => separémoslos (let's separate them)
lo contar (to tell it) => contadlo (tell it)
In the negative imperative (also called prohibitive imperative), none of this applies since enclisis should not be used.
no separarse (not to separate) => no nos separemos (let's not separate)
Stress Modification
You will have already noticed something through the previous examples: the modification of stress in the pronominal form of the imperative. Indeed, the tonic stress is always located in the same place when a verb has an enclisis. This means that to prevent the enclisis from modifying the position of the stress in the verb, an accent is added.
ayudar (to help) => (él) ayuda (he helps) => ayúdame (help me)
escuchar (to listen) => escuchándole (listening to him/her)
decir (to say) => decirlo => decírselo
enseñar (to teach) => enseñándolo => enseñándoselo
