Etiquette of Invocation's (Duas)

• Sincere Intention
• To begin with praise and glorification of Allah's and to send blessings on the Prophet صلي الله عليه و سلم and to end the dua in the same manner.
• To invoke with the certainty that it will be accepted 
• Do not ask from anyone other than Allah
• Invoke for oneself first and then for others.
• Seek forgiveness from Allah while acknowledging ones sins
• Acknowledge the blessings of Allah upon oneself and to show gratitude.
• To make dua with full concentration as Allah does not accept a dua of a heedless heart.

The times of acceptance of Invocation (Duas)

• At the end of obligaratory (Farz) prayers.
• Between the Azan and the Iqamaat. 
• At the time of Tahajud.
• In prostration.
• When it is raining.
• Traveling on a journey.
• A specific time on Friday.
• In the battlefield.
• At the time of pre-dawn meal (sehri)
• When fasting
• When opening the fast.
• The night of power and destiny.
• When drinking Zamzam.
• On the day of Arafat and while standing in the plain of Arafat.
• After recitation of The Quran. 

It is proved from Ahadith that Allah(swt) accepts the invocation at these times.

Why Invocation is not accepted?

Once Ibrahim bin Adham was asked, we invoke Allah but our invocations are not answered. What is the reason for this? So he replied:

• You recognized Allah but did not give his right.
• You read the Quran but did not act upon it.
• You claimed to love the prophetصلي الله عليه و سلم but did not act upon his sunnah.
• You desired paradise but did not do those deeds in order to enter it.
• You claimed to have enmity for shaytaan but did not oppose him.
• You acknowledged the reality of death but did not prepare for it.