Common Supplication in Month of Sha’aban
Imam Ali bin Hussein Al Zanul Abideen (a.s) told his companions: "The Holy Prophet (PBUH) used to observe fast during the whole month of Sha’aban. Therefore whosoever, in love of the Holy Prophet (PBUH), wishes to seek nearness to Allah and receive bounties, favors and rewards in this world and in the Hereafter, must connect Sha’aban with Ramadhan (in the matter of fasting and special prayers)".
1) Recite 70 times:
I seek forgiveness of Allah, and, repentant, beseech Him.
I seek forgiveness of Allah who is "There is no God save He", the Beneficent, the Merciful; the Ever living, the Eternal, and I turn repentant to Him
According to narrations, the best supplications and invocations that are advisably recited in Sha’aban are the prayers of seeking forgiveness of Almighty Allah (i.e. istighfar). Hence, to seek Almighty Allah’s forgiveness seventy times a day in Sha’aban is equal to seeking His forgiveness seventy Thousand times a day in the other months.
2) Give Alms/Charity in God’s name.
Imam Sadiq was asked "What are the best deeds that should be done in Sha’aban?" The Imam (a.s) answered, "Almsgiving and seeking forgiveness are the best deeds in Sha’aban. Verily, if anyone of you gives alms in Sha’aban, Almighty Allah will breed that alms in the very same way as you breed your small camels. Hence, these alms will be as huge as Mount Uhud on the Resurrection Day."
3) Recite the following 1000 times.
There is no god save Allah. We do not worship save "He" alone, making religion pure for Him (only), however much the disbelievers be averse.
4) On every Thursday Fasting is recommended & Recite two Rakaat Namaz.
In every Rakaat, after the recitation of Surah Hamd (The Opening), recite Surah Ikhlaas (The Purity)100 times. After the Salaam recite Salawat 100 times. Send blessings upon Mohammad and the household of Mohammad. In this respect, a Hadith reads that the heavens decorate themselves each Thursday in Sha’aban and the angels pray Almighty Allah, saying, "O our God: (please do) forgive him who observe fasting on this day and respond to his prayers."
The Holy Prophet (PBUH) is also reported as saying, "If one observes fasting each Monday and Thursday in Sha’aban, Almighty Allah will settle forty of his needs—twenty appertained to the worldly life and twenty to the Hereafter.
5) Recite the Special Salawat taught by Imam Ali bin Hussein Al Zanul Abideen (a.s).
6) Recite Munajat e Shabaniyah with presence of heart.
* Source: duas.org