Reciting Surah-al-Yaseen, Surah-as-Saffat and the following supplication (du'a) eases the tribulation during death:
لا إله إلا الله الحليم الكريم. لا إله الله العلي العظيم. سبحان الله رب السموات السبع ورب الأرضين السبع وما فيهن وما بينهن وما فوقهن وماتحتهن وهو رب العرش العظيم والحمد لله رب العالمين.
Shaikh Sadooq narrates from Imam Ja'far-as-Sadiq (A.S.) that he said, "For the person who fasts on the last day of the month of Rajab, Allah will save him from the after effects of death". Fasting on the 24th of Rajab carries great reward (Sawab). One of it's merits is that when the Angel of death comes to remove his spirit (Rooh), he comes in the form of a handsome youth carrying a bowl of the pure drink (Sharabe Tahoora) and offers him to drink. The dying person does so and dies in peace.
The Holy Prophet (S.A.W.S.) says that if a person recites four unit (Rak'at) Namaz on the night of 7th Rajab in a manner that in each unit (Rak'at) after Surah-al-Hamd recites thrice Surah-at-Tawheed, once Surah-al-Falaq, and once Surah-an-Naas. After finishing the Namaz, sends Salawat on Us and recites ten times Tasbeehate Arba.
سبحان الله والحمد لله ولا اله إلا الله والله اكبر