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.
Recite Special Ziarat of Imam Husayn(as) for 15 Shaban 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 :-
السَّلامُ عَلَيْكَ يَا أَبَا عَبْدِ اللّه السَّلامُ عَلَيْكَ وَرَحْمَةُ اللّه وَبَرَكَاتُهُ
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.
Recite Dua Kumayl for Seeking forgiveness.
In Hadith, it is mentioned that Kumayl ibn Ziyad said, "I was sitting with my master Amir al-Mominin ‘Ali ibn Abu Talib (peace be upon him) in Masjid Kufa and a group of companions were also sitting with him. One of them asked him what the meaning of the verse 'Whereupon every wise command is made clear.' (Surah ad-Dukhan, Verse 4) The Imam (peace be upon him) replied, The meaning of this is the night of the 15th of Sha‘ban. I swear by the One who holds the life of ‘Ali in His hands there is not a single servant of Allah except that all the good and bad that will reach him in this year is divided up and handed out on the 15th of Sha‘ban and this good and bad will continue from the 15th of Sha‘ban until the next year on the same night. The servant who stays up this night and recites the Du‘a of Khidr will have his supplications answered." This dua taught to Kumayl ibn Ziad is now known popularly as Dua e Kumayl.
Seek closeness to Imam al-Mehdi (may Allah hasten his return) the Hujjah of our Time; Wali al-‘Amr; the Greatest Secret (of Allah); the possessor of the divine Occultation and inviter to the message of the Prophet; the Successor of all Prophets and the Successor of all Successors of the Prophets; the physical manifestation of the Justice of Allah; the Flag of Guidance; the one who will destroy all corruption and oppression and those who oppose the truth; the destroyer of the enemies of Allah - the misguided and the disbelievers; the one who will purify the Earth of deviation and worship of the self; the greatest sign of Allah; the one who acts as the connection between the heavens and the earth; our Imam, Master and Qaim, al-Mahdi - may my soul and the souls of all of those in the universe be sacrificed for him.
Stay busy in Ziyarat, Munajat and asking our desires and complaining of our separation from our awaited Imam.
Write an Ariza(Letter)to Imam.
Our supplications and Salat should always be performed with the thought in the back of our minds of the distance from our leader however we should also keep in mind and be thankful to Allah swt that we are blessed with such a guide. Recite the duas relating to the Imam (atfs) Dua Nudba , Isteghasa & Ziarat Aale Yasin of the Ahlulbayt(as).
It is recommended to mention Almighty Allah by the following invocation one hundred times so that one’s past acts of disobedience to Almighty Allah will be forgiven and one’s worldly and religious needs will be settled:
All glory be to Allah;
all praise be to Allah;
وَلا إلهَ إلاَّ اللّهُ،
wa la ilaha illa allahu,
there is no god save Allah;
Shaykh al-Tusy in ‘Misbah al-Mutahajjid’, has narrated a Hadith about the merits of the fifteenth night of Sha`ban entailing that Abu-Yahya asked Imam Ja`far al-sadiq (a.s) about the best of supplications at this night. The Imam (a.s) instructed him saying: “After you finish the obligatory `Isha' Prayer, you may offer a two Rak`ah prayer in the first of which you should recite Surah of al-Fatihah and Surah of al-Kafirun and in the second you should recite Surah of al-Fatihah and Surah of al-Tawhid. When you accomplish the prayer,
you may repeat (the phrase of) ‘subhanallah’ thirty-three times,
(the phrase of) ‘alhamdulillah’ thirty-three times,
and (the phrase of) ‘allahu-akbar’ thirty-four times.
faya la ilaha illa anta aj`alny fi hadhihi allaylati mimmn nazarta ilayhi farahimtahu
So, O He save Whom there is no god: (please) include me at this night with those at whom You have looked and thus You have mercy upon them;
وَسَمِعْتَ دُعَاءَهُ فَأَجَبْتَهُ،
wa sami`ta du`a‘ahu fa-ajabtahu
and with those whose prayers have been heard by You and thus You have responded to them;
وَعَلِمْتَ اسْتِقَالَتَهُ فَأَقَلْتَهُ،
wa `alimta astiqalatahu fa-aqaltahu
and with those whose true repentance has been admitted by You and thus You have accepted it;
It is recommended to do the prostrations and say the supplications that are reported from the Holy Prophet (a.s). One of these is that Shaykh al-Tusiy has narrated on the authority of Hammad ibn on the authority of Aban ibn Taghlib that Imam Ja`far al-Sadiq (a.s) recounted the following:
It was the fifteenth night of Sha`ban when the Holy Prophet (a.s) was with A'ishah, his wife. At midnight, the Holy Prophet (a.s) left the bed. When `ª'ishah woke up and could not find the Holy Prophet (a.s), she felt jealous and Thought that he joined one of his other wives. ª'ishah searched for the Holy Prophet (a.s) in all the rooms of his other wives but she found him prostrating himself on the ground As she approached, she heard him saying:
سَجَدَ لَكَ سَوَادِي وَخَيَالِي،
sajada laka sawady wa khayali
Prostrating before You are my body and my shadow
وَآمَنَ بِكَ فُؤَادِي،
wa amana bika fu´adi
and my heart is in full faith of You
هذِهِ يَدَايَ وَمَا جَنَيْتُهُ عَلَى نَفْسِي،
hadhihi yadaiya wa ma janaytuhu `ala nafsi
These are my two hands and this is what I have committed against myself,
يَا عَظِيمُ تُرْجَى لِكُلِّ عَظِيمٍ
ya `azimu turja likulli `azimin
O the All-great: You are hoped for all enormous things;
اغْفِرْ لِيَ الْعَظِيمَ
aghfir liya al`azima
Please, forgive me my serious offences
فَإنَّهُ لا يَغْفِرُ الذَّنْبَ الْعَظِيمَ إلاَّ الرَّبُّ الْعَظِيمُ.
fa’innhu la yaghfiru aldhdhanba al`azima illa alrrabbu al`azimu
because none can forgive the serious sin except the All-great Lord.
The Holy Prophet (a.s) then raised his head and then prostrated himself again, saying:
wa salaha `alayhi amru al-awwalina wal-akhirina
and has made active all the affairs of the past and the coming generations
مِنْ فُجْأَةِ نَقِمَتِكَ،
min fuj-ati naqimatika
against Your sudden chastisement
وَمِنْ تَحْوِيلِ عَافِيَتِكَ،
wa min tahwili `afiyatika
and against withdrawing the good health that You have granted me
وَمِنْ زَوَالِ نِعْمَتِكَ.
wa min zawal-i ni`matika
and against the vanishing of Your bounties.
اللّهُمَّ ارْزُقْنِي قَلْباً تَقِيّاً نَقِيّاً
allahumma arzuqny qalban taqiyyan naqiyyan
O Allah: (please) grant me a heart that is pious and pure,
وَمِنَ الشِّرْكِ بَرِيئاً
wa mina alshshirki bari’an
and is released from polytheism,
لا كَافِراً وَلا شَقِيّاً.
la kafiran wa la shaqiyyan
and is neither atheist nor unhappy.
The Holy Prophet (a.s) then attached his face to the ground and said:
عَفَّرْتُ وَجْهِي فِي التُّرَابِ
`affartu wajhy fi altturabi
I am putting my face on the ground
وَحُقَّ لِي أَنْ أَسْجُدَ لَكَ
wa huqqa li an asjuda laka
and it is my duty to prostrate myself before You
Holy Prophet (a.s) then said, “Do you know what this night is? This is the night of the half of Sha`ban. At this night, shares of provisions are distributed, ages are decided, and the pilgrims are appointed. Verily, Almighty Allah, at this night, forgives as many of His creatures as the hairs of the goats of Kalb Tribe. Almighty Allah also orders angels to descend to the earth, to Makkah, at this night.”
It is recommended to offer the prayers that are dedicated to this night. As a matter of fact, these prayers are many. One of them is that which is reported by Abu-Yahya al-San`aniy, as well as other thirty trustworthy individuals, from Imam Muhammad al-Baqir (a.s) and Imam Ja`far al-Sadiq (a.s) as follows:
At the night of the half of Sha`ban, you may offer a four Rak`ah prayer in each Rak`ah of which you may recite the Surah of al-Fatihah once and the Surah of al-Tawheed one hundred times. After accomplishment, you may say the following supplication:
اللّهُمَّ إنِّي إلَيْكَ فَقِيرٌ،
allahumma inni ilayka faqirun
O Allah: I am in need for You,
وَمِنْ عَذَابِكَ خَائِفٌ مُسْتَجِيرٌ.
wa min `adhabika kha’ifun mustajirun
and I am fearful of You and seeking Your shelter against Your chastisement.
اللّهُمَّ لا تُبَدِّلِ اسْمِي،
allahumma la tubaddil ismi
O Allah: (please) do not erase my name,
وَلا تُغَيِّرْ جِسْمِي،
wa la tughayyir jismi
and do not change my body,
وَلا تَجْهَدْ بَلائِي،
wa la tajhad bala’y
and do not increase my ordeals,
وَلا تُشْمِتْ بِي أَعْدَائِي،
wa la tushmit by a`da’y
and do not make my enemies rejoice at my misfortune.
أَعُوذُ بِعَفْوِكَ مِنْ عِقَابِكَ،
a`udhu bi`afwika min `iqabika
I resort to Your pardon against Your punishment,
وَأَعُوذُ بِرَحْمَتِكَ مِنْ عَذَابِكَ،
wa a`udhu birahmatika min `adhabika
and I resort to Your mercy against Your chastisement,
وَأَعُوذُ بِرِضَاكَ مِنْ سَخَطِكَ،
wa a`udhu biridaka min sakhatika
and I resort to Your pleasure against Your wrath,
وَأَعُوذُ بِكَ مِنْكَ،
wa a`udhu bika minka
and I resort to You from You
Enormous be the praise of You
أَنْتَ كَمَا أَثْنَيْتَ عَلَى نَفْسِكَ
anta kama athnayta `ala nafsika
You are as exactly as You have praised Yourself,
وَفَوْقَ مَا يَقُولُ الْقَائِلُونَ.
wa fawqa ma yaqulu alqa’iluna
and above all that which is said about You.