The Holy Prophet (PBUH) had said that during the night of 15th Sha’aban the Almighty takes decisions in the matters of sustenance, life and death and welfare of the people. According to the Imam Muhammad Baqir (a.s) and Imam Jafar Sadiq (a.s) Allah has promised to fulfill every legitimate desire put forward to Him tonight.
During this night Allah bestows on HIS people from HIS bounty & forgives them out of HIS grace & generosity. Of the blessings of this night is that, at the dawn of this night, was born the Leader of the Time Imam Mahdi (a.s) in Samarra -Iraq in the yr 255 AH.
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.
"Therefore, stay awake this night in prayer and worship and encourage your Ummat 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."
1) Recite 100 times:
Subh’aanallah Walh’amdu Lillah Wa-Laa Ilaaha Illallah Ho Wal Allahu Akbar
2) Take Ghusl (Bath) with the thought of washing away sins & as if its your last Ghusl.
3) Recite 100 times 'Astaghfirullah ' with attention to seeking forgiveness.
4) Recite Ziyaraat of Imam Hussein (a.s) & Special Ziyaraat of Imam Hussein (a.s) for 15 Sha’aban as all the Prophets& Angels visit the Imam on this night.
As a short salutation, one may go to the terrace/elevated place, look left, right & towards the sky & recite:
Assalamu Alalika Ya Aba Abdillah Assalamu Alaikum wa Rahmatullah e wabarakatoh.
Peace be upon you; O Aba-`Abdullah! Peace and Allah’s mercy and blessings be upon you.
5) Recite prayer of Jafar-e-Tayyar
6) Recite Kumayl supplication for seeking forgiveness.
* Source: duas.org