And your Lord says, "Call upon Me; I will respond to you." Indeed, those who disdain My worship will enter Hell [rendered] contemptible.
Jubair bin Nufair narrated that `Ubadah bin As-Samit narrated to them that, the Messenger of Allah (sallallaahu alayhi wa sallam) said:
“There is not a Muslim upon the earth who calls upon Allah with any supplication, except that Allah grants it to him, or He turns away from him the like of it in evil; as long as he does not supplicate for something sinful, or the severing of the ties of kinship.” So a man from the people said: “What if we should increase (in it)” He (sallallaahu alayhi wa sallam) said: “(With) Allah is more.”
Jaami' al-Tirmidhi Hadiith No. 3573
Du'aa is worship and has a far reaching effect. Had it not been the case, Allaah would not have ordered us to make du'aa. How many problems have been lifted by Allaah because of du'aa!
The Qur'aan and Sunnah are both filled with 'ad'iyah (plural of du'aa).
The one who does not make du'aa has closed the doors of abundant good upon himself. No one should do this to themselves. No sane person would close the doors of good upon himself.
The 'aaadaab of du'aa
If you want your du'aa to be answered, then you must ensure that your food, place to live, clothing, and all that you have is halaal. The evidence for this is the following hadith:
Narrated Abu Hurairah that the Messenger of Allah (sallallaahu alayhi wa sallam) said:
"O you people! Indeed Allah is Tayyib (good) and He does not accept but what is good. And indeed Allah ordered the believers with what He ordered the Messengers.
He said: 'O you Messengers! Eat of the good things and do righteous deeds. Verily I am well acquainted with what you do.'
And He said: 'O you who believe! Eat from the good things We have provided you.'
He said: "And he mentioned a man: 'Who is undertaking a long journey, whose hair is dishevelled and he is covered with dust. He raises his hands to the heavens and says: "O Lord! O Lord!" Yet his food is from the unlawful, his drink is from the unlawful, his clothing is from the unlawful, and he was nourished by the unlawful. So how can that be accepted?'"
Jaami' al-Tirmidhi hadiith No. 2989
Your voice should not be loud when you make du'aa. Keep the following Verse in mind:
Call upon your Lord in humility and privately; indeed, He does not like transgressors.
Also keep in mind the following hadiith:
Narrated Abu Musa:
While we were with Allah's Messenger (sallallaahu alayhi wa sallam) in a holy battle, we never went up a hill or reached its peak or went down a valley but raised our voices with Takbiir.
Allah's Messenger (sallallaahu alayhi wa sallam) came close to us and said, "O people! Don't exert yourselves, for you do not call a deaf or an absent one, but you call the All-Hearing, the All-Seer." The Prophet (sallallaahu alayhi wa sallam) then said, "O `Abdullah bin Qais! Shall I teach you a sentence which is from the treasures of Paradise? ( It is): 'La haula wala quwata illa billah. (There is neither might nor power except with Allah).
Sahiih al-Bukhaari Hadiith No. 6610
Allaah is the All-Hearing. He is the All-Seeing. You do not have to shout when you make du'aa. Make du'aa with humility.
Raise your hands when you make du'aa. The evidence for this is present in the following hadiith:
Salman al-Farsi narrated that the Prophet (sallallaahu alayhi wa sallam) said:
"Indeed, Allah, is Hayy, Generous, when a man raises his hands to Him, He feels too shy to return them to him empty and rejected."
Jaami' al-Tirmidhi Hadiith No. 3556
Most scholars of hadiith have said the above hadiith is established and authentic. Some have said it is weak.
The Kuwaiti Encyclopedia of Fiqh
Volume 20 Page 259