Laylat al-Qadr is a great night, the greatness of which Allah referred to in His Book, in the following passages:
We sent it (this Quran) down on a blessed night. Verily, We are ever warning [mankind that Our Torment will reach those who disbelieve in Our Oneness of Lordship and in Our Oneness of worship]. Therein (that night) is decreed every matter of ordainments” (Ad-Dukhan 44:3-4)
Verily, We have sent it (this Quran) down in the Night of Al-Qadr (Decree). And what will make you know what the Night of Al-Qadr (Decree) is? The Night of Al-Qadr (Decree) is better than a thousand months (i.e. worshipping Allah in that night is better than worshipping Him a thousand months). Therein descend the angels and the Ruh [Jibril (Gabriel)] by Allah’s Permission with all Decrees. (All that night), there is peace (and goodness from Allah to His believing slaves) until the appearance of dawn. (Al-Qadr 97:1-5)
It is a night which Allah, may He be glorified and exalted, has made superior to other nights, and He has told us that good deeds during this night are better than good deeds during one thousand months. This is a great virtue. He also singled it out by sending down the Quran during it, and describing it as a blessed night, on which is decreed what will happen during the coming year. This is an important distinction of this night.
The Prophet (blessings and peace of Allah be upon him) used to strive hard during the last ten days of Ramadan in a manner in which he did not do during other times, seeking Laylat al-Qadr.
It is the best of nights, because what has been reported concerning its virtues has not been reported concerning other nights. So, it is the best of nights, because of what it includes of these great distinctions. This is by the mercy of Allah, may He be exalted, and His kindness to this ummah, as He singled it out for this great night.
Below are some good deeds to be observed in this night:
Praying qiyam al-Layl
It is recommended to make a long qiyam prayer during the nights on which Laylat al-Qadr could fall. This is indicated in many Hadiths, such as the following:
Abu Dharr (may Allah be pleased with him) relates: “We fasted with Allah’s Messenger (peace be upon him) in Ramadan. He did not lead us in Qiyam (Night Vigil Prayer) at all until there were seven nights of Ramadan left. Then he stood with us (that night, in Prayer) until one third of the night had passed. He did not pray with us on the sixth. On the fifth night, he prayed with us until half of the night had passed. So we said, ‘Allah’s Messenger! Wouldn’t you pray with us the whole night?’ He replied: ‘Whoever stands in Prayer with Imam until he (the Imam) concludes the Prayer, it will be recorded for him that he prayed the whole night…” (Ibn Abi Shaybah, Abu Dawud and At-Tirmidhi)
Abu Dawud mentioned: “I heard Ahmad being asked, ‘Do you like for a man to pray with the people or by himself during Ramadan?’ He replied, ‘Pray with the people’ I also heard him say, ‘I would prefer for one to pray Qiyam with Imam and to pray Witr with him as well, for the Prophet (peace and blessings be upon him) said: “When a man prays with the Imam until he concludes, he’ll earn the reward of praying the rest of that night.”
Abu Hurayrah (may Allah be pleased with him) narrated that the Prophet (peace be upon him) said: “Whoever stands (in Qiyam) in Laylatal-Qadr (and it is facilitated for him) out of faith and expectation of Allah’s reward, will have all of his previous sins forgiven.” (Reported by Al-Bukhari and Muslim). The phrase “and it is facilitated for him”, according to the version narrated by Ahmad, on the authority of `Ubadah Ibn As-Samit, means that a person is permitted to be among the sincere worshippers during that blessed night.
It is also recommended to make extensive supplication on this night. Aishah (may Allah be pleased with her) reported that she asked the Prophet (peace be upon him) “O Messenger of Allah! If I knew which night is Laylat al-Qadr, what should I say during it?” And he instructed her to say: “Allahumma innaka `afuwwun tuhibbul `afwa fa`fu `annee (O Allah! You are Oft-Forgiving, and you love forgiveness. So forgive me).” (Ahmad, Ibn Majah and At-Tirmithi)
Abandoning worldly pleasures for the sake of worship
It is further recommended to spend more time in worship during the nights on which Laylat al-Qadr is likely to be. This calls for abandoning many worldly pleasures in order to secure the time and thoughts solely for worshipping Allah.
This is based on the following hadith narrated by Aishah (may Allah be pleased with her): “Upon entering into the last ten (of Ramadan), the Prophet (peace be upon him) would tighten his Izar (i.e. he stayed away from his wives in order to have more time for worship), spend the whole night awake (in Prayer), and wake up his family.” (Al-Bukhari and Muslim)
She also said: “Allah’s Messenger (peace and blessings be upon him) used to exert more efforts (in worship) on the last ten than on other nights.” (Muslim)
With regard to specifying a night of Ramadan as being Laylat al-Qadr, this lacks clear evidence. However, the odd-numbered nights during the last ten nights are more likely than others, as reported in the hadiths of the Prophet (peace be upon him).
Source: www.aboutislam.net, www.Islamqa.info