are appended as suffixes to some grammatical forms:
a) Usually the pronouns are appended
to infinitive verbs, it is still considered correct
not to append them:
With a positive imperative (Do it!)
it is obligatory to append the pronouns. In an negative
imperative they are not appended.
In constructions with gerunds, the
pronouns are to be appended.
In constructions with estar + gerund it can be appended
but it's not obligatory.
More details on gerunds you'll
find in chapter
More details on imperative forms you'll find in chapter