Shaykh Abdur-Razzaaq bin Abdul-Muhsin Al-Badr, may Allaah perserve him and his father, explains matters of Du’aa, its importance and benefits derived from it.
a small excerpt from the book:
He who reviews the Qur’aan will find that the Book of Allaah, the Mighty and Majestic, is replete with many verses and a number of texts indicating the virtue of Du’aa and the loftiness of its status. When you read the Qur’aan, you will find that the first Soorah with which the book of Allaah, the Mighty and Majestic, begins with it; Soorah Al-Faatihah contains this tremendous act of worship, and the last of the Qur’aan Soorah An-Naas as well, contains this tremendous act of worship.
So the Book of Allaah, the Mighty and Majestic, begins with Du’aa and ends with it. The Du’aa, which is within Al-Faatihah, is the greatest of supplications hands down. (It contains) asking Allaah, the Blessed and High, for guidance to the straight path and that the servant avoids the paths of those who are astray and those upon whom is the Anger of Allaah. The last of the Book of Allaah, the Mighty and Majestic, contains the Du’aa of seeking refuge with Him, Glorified and Exalted be He, from the evil of the one who whispers and withdraws; the one who whispers into the hearts of mankind; from the Jinn as well as men, in order to make them deviate from the straight path of Allaah and the upright way.
Allaah informs us that Shaytaan says:
Then I will come to them from before them, and behind them, from their right and their left, and You will not find most of them as thankful ones (i.e., they will not be dutiful to You).
So there is no firmness upon the straight path of Allaah, nor safety from the accursed Shaytaan-who calls mankind to deviation from the straight path-except by way of Du’aa and seeking refuge with Allaah, the Majestic and High; and a good manner of taking refuge with Him. This beginning and ending contain an indication of the importance of Du’aa from different perspectives; and the need of mankind for Du’aa to be firm upon the straight path of Allaah. When you reflect upon the other verses of the Qur’aan, you find the great status of Du’aa and lofty station of it within the Qur’aan.
Many verses within the Qur’aan contain the command to make Du’aa and incitement towards it; clarification of its virtue and its status and (mention of) that which Allaah, the Blessed and High, has prepared for its people from magnificent reward and abundant bounty and general good within the Dunyaa and the next life. You see, within the Qur’aan, supplications of the Prophets and the righteous from the servants of Allaah and their good connection with Allaah, the Majestic and High. Allaah has said:
Verily, they used to hasten on to do good deeds, and they used to call on Us with hope and fear, and used to humble themselves before Us.
And Allaah also said:
Their sides forsake their beds, to invoke their Lord in fear and hope.
Likewise, Allaah said:
And keep yourself (O Muhammad0) patiently with those who call on their Lord (i.e. your companions who remember their Lord with glorification, praising in prayers, etc., And other righteous deeds, etc.) morning and afternoon seeking His Face. 
Hence, Allaah, the Mighty and Majestic, has commended the Prophets and the righteous from amongst His servants for their concern with Du’aa, and their giving it due importance; and the excellent manner of taking refuge with Allaah, the Majestic and High. He informed within these verses that He responds to them and that He, Glorified and Exalted be He, will answer the one who supplicates to Him and give Him that which he asks for; and he will not reject a believer who calls upon Him.
 (Al-A’raf 7:17)
 (Al-Anbiya 21:90)
 (As-Sajdah 32:16)
 (Al-Kahf 18:28)