The Holy Prophet (sa.) had said that during the night of 15th Shaba'an the Almighty takes decisions in the matters of sustenance, life and death and welfare of the people. Next to the “Night of Qadr” the night of 15th Sha’baan is the most auspicious night (also known as “night of Baraat”). According to the Imams Muhammad bin Ali Al Baqir (as.) and Jaa’far bin Muhammad As Sadiq (as.) Allah swt has promised to fulfill every legitimate desire put forward to Him tonight. During this night Allah (swt) bestows on HIS people from HIS bounty & forgives them out of HIS grace & generosity.
Ahadith in the book Iqbalul A‘mal "Therefore, stay awake this night in prayer and worship and encourage your Ummah to also keep awake this night in order to get closer to Allah (Glorified and Exalted is He) through their actions since this is a noble night. This is a night in which not a single person supplicates to Allah except that his prayers are accepted. Nobody asks for a single thing on this night except that it will be given to him. No one asks Allah for forgiveness except that his sins are wiped out. No one turns in repentance to Allah except that He accepts their repentance. Whoever is deprived of the goodness of this night has definitely been deprived of something great."
Almighty Allah has chosen this night for the Ahl ul-Bayt, in the same way as He has chosen the Qadr Night for our Prophet(peace be upon him and his Family.)
The first thing that that Salik (the Wayfarer on the path towards Allah, Glorified and Exalted is He) must perform on this night is that he must remove the material pleasures and enjoyments of this world from in front of his eyes (and from his heart) and in order to make the most of this special night and ensure that all of his actions are performed properly, he must think to himself that tonight is his last night on this Earth (meaning that tomorrow he shall die) and thus, he will no longer have the opportunity to perform any more good deeds and that tomorrow the Day of Judgment will take place.
It is advisable to stay awake during this full night in prayer as it has many rewards, hadith has confirmed that as for one who spends this whole night with acts of worship, his heart will not die when other hearts die.
As a final act on this night, take account for his own soul and the actions he has performed during the year. A person should sincerely and properly ponder and reflect upon his actions during this year and ask repentance for his previous acts of transgression since it is only those people whom Allah (Glorified and Exalted is He) has protected from committing sin and error who are free of this pollution. If a person sees that he has little to no sins on his record then he should compare this to one of the most insignificant blessings that Allah (Glorified and Exalted is He) has given him and weigh the two on the scales of justice that with his trivial acts of good, has he been able to repay Allah (Glorified and Exalted is He) back for all the goodness He has provided?
If he realizes that he has sins and transgressions on his record, then he must resort to Tawassul to the Ma‘sumin (blessings be upon all of them) to make up for his shortcomings.
He should address the infallible ones by saying following:- "O you who Allah has placed between Himself and His servants! O you who are the protectors of His revelation. I ask you by the position that you have that you look towards me, a sinful servant, with your eyes
of mercy the one who has been lax in his worship, who possesses nothing and is nothing. Have mercy upon me and request Allah to accept me and to be pleased with me on this night and to permit me to be benefit from your prayers and supplications and to
permit me to take advantage of your intercession and to be classified as your Shi‘a. In addition, ask Allah to grant me with the reward of goodness and guidance from you. Pray that He makes me of strong will and that I am successful in performing good deeds for my religion, my life here and my next life".
Source al-mubin.org