Just as du’a has certain pre-conditions and etiquettes attached to it, there are also certain acts that are discouraged during du’a.
Some of these acts are extremely serious, such as calling on other than Allah, which is an act of shirk or making partners with Allah, and takes one outside the fold of Islam. Others, such as making improper tawassal, or means of seeking nearness to Allah, can damage one’s imaan.
For these reasons, it is very important that we understand what not to do when making du’a, as much as it is to understand what we should do.
Discouraged acts when making du’a include: poetry or excessive rhyming of words; asking for things that are prohibited; exaggerating; calling on other than Allah in the du’a; making du’a for something that is known to already have been decreed; making du’a whilst not expecting a response; to pray only for worldly matters neglecting the Hereafter; to use a Name or Attribute of Allah that is not mentioned in the Qur’an and Sunnah; to ask for punishment; to make du’a against oneself and one’s family; to curse someone; to ask Allah to limit His Infinite Mercy; to pray for death or evil; to look upwards during the prayer; to imply that one will not ask Allah anything else after this; to improperly use Arabic and make frequent mistakes; to rely on others to make du’a for you; to cry excessively out loud in public; to make excessively long congregation du’as and to mention only oneself if you are the Imam.