On the first Thursday of Rajab there is a sunnah prayer between Isha and midnight that consists of 12 rakats done in pairs (i.e. after each two rakats you must give salams).
In each rakat you must recite Al-Fatiha x1, Surat-ul-Qadr x3, and Surat-ul-Ikhlas x3. After you have finished you must recite salawat x 70.
Then make sujud (prostration) and while in sujud recite 70x Subbuuhan qadduusun rabbul malaaikati warrah.
After this when you are sitting recite 70x Rabbighfir warham wa tajaawaz’amma ta’lamu inaka antal-a-azzul akramu then make your dua.
Then make sujud one more time and once again recite 'Subbuhan qaddusun rabbul Malaakati waarah' a few times and make your dua again.
The Prophet Muhammad (s.a.w.s) has said: “There is no one who prays this prayer that Allah Almighty does not forgive their sins even if they are as many as all the bubbles in the sea, as many as the grains of sand in the deserts, as heavy as the mountains and as many as the leaves on all the trees and Allah will give them the sufa'it (power, gift) to bring 700 of their family to Paradise on the Day of Judgement even though they were supposed to go to hell.”
Laylat ul-Isra (the 27th of Rajab): This is the night when the Holy prophet was taken up to the heavens to meet his Lord Allah Almighty. It is also known as the night of Ascension. It is the practise of the learned ones to pray 20 rakats between Magrib and Isha. This prayer can be prayed either 2 rakats or 4 rakats at a time reciting 20 surah ul-Ikhlas in each rakat. When finished you should recite out loud 100 Istighfar and 100 salawat sharifah.
The Prophet Muhammad (s.a.w.s) said “On this night 70,000 angels descend with Allah’s mercy and nur (light) searching for houses whose occupants are awake and engaged in Dhikr. The angels are then commanded to pour Allah’s mercy and blessings upon such houses and their occupants."