Ramadan Advice
All praises is for Allah and blessings on his Prophet, Muhammad (SAWS).
The Ramadaan fast and other acts of worship are not valid unless accompanied by the proper intention, because the Prophet (peace and blessings of Allaah be upon him) said: "Actions are but by intentions, and everyone shall have but that which he intended…" (Narrated by al-Bukhaari, 1; Muslim, 1907)
The intention is subject to the condition that it be made at night, before the dawn comes, because the Prophet (peace and blessings of Allaah be upon him) said: "Whoever does not intend to fast before dawn, there is no fast for him." Narrated by al-Tirmidhi, 730. According to a version narrated by al-Nasaa'i (2334): "Whoever does not intend to fast from the night before, there is no fast for him." Classed as hasan by al-Albaani in Saheeh al-Tirmidhi, 573. What is meant is that whoever does not intend to fast and resolve to do so from the night before, his fast is not valid.
The intention (niyyah) is an action of the heart. The Muslim should resolve in his heart that he is going to fast tomorrow. It is not prescribed for him to utter it out loud and say, "I intend to fast" or "I will fast tomorrow" or other phrases that have been innovated by some people. The correct intention is when a person resolves in his heart that he is going to fast tomorrow.
With regard to sahoor, there is no specific du'aa' to be said at this time. What is prescribed is to say Bismillah at the beginning and to praise Him when one stops eating, as should be done at every meal.
The recommended du'a narrated in the Sunnah which the fasting person may say at the time of breaking the fast is "Dhahaba al-zama'u wa abtalat al-'urooq wa thabat al-ajru in sha Allaah (Thirst has gone, the veins are moist, and the reward is assured, if Allaah wills)." He may also say whatever du'aa' he wants, not because that is mentioned specifically in the Sunnah, but because it is the end of an act of worship, and it is prescribed for the Muslim to say du'aa' in that case.
Saying du'aa' after doing acts of worship is deeply rooted in sharee'ah, such as making du'aa' after praying and after completing the rituals of Hajj. Fasting is not excluded from that in sha Allaah. Allaah mentioned the verse of du'aa' and encouraged du'aa' among the verses that speak of fasting, as Allaah says (interpretation of the meaning):
"And when My slaves ask you (O Muhammad) concerning Me, then (answer them), I am indeed near (to them by My Knowledge). I respond to the invocations of the supplicant when he calls on Me (without any mediator or intercessor). So let them obey Me and believe in Me, so that they may be led aright" [al-Baqarah 2:186]
The first is that they should obey His commands to worship Him and seek His help. The second is that they should believe in His Lordship and Divinity, and that He is their Lord and their God. Hence it is said that response to a person's du'aa' is indicative of the soundness of his belief and the perfection of his obedience, because the verse of du'aa' ends with the words (interpretation of the meaning): "So let them obey Me and believe in Me, so that they may be led aright"