Laylatul-Qadr is the most blessed night. A person who misses it has indeed missed a great amount of good. If a believing person is zealous to obey his Lord and increase the good deeds in his record, he should strive to encounter this night and to pass it in worship and obedience. If this is facilitated for him, all of his previous sins will be forgiven.
It is recommended to make a long Qiyaam prayer during the nights on which Laylat -ul -Qadr could fall. This is indicated in many Ahaadeeths, such as the following:
Abu Dharr (radiyallaahu`anhu) relates: "We fasted with Allah's Messenger (sallallaahu`alaihiwasallam) in Ramadhaan. He did not lead us (in qiyaam) at all until there were seven (nights of Ramadhaan) 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 the Imaam until he (the Imaam) concludes the prayer, it is recorded for him that he prayed the whole night.'…" [Recorded by Ibn Abi Shaybah, Abu Dawud, at-Tirmidhi (who authenticated it), an-Nasa'i, Ibn Majah, at-Tahawi (in Sharhu Ma`an il-Athar, Ibn Nasr, al-Faryabi, and al-Baihaqee. Their isnaad is authentic.]
[Point of benefit: 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 (qiyaam) with the Imaam and to pray Witr with him as well, for the Prophet (sallallaahu`alaihiwasallam) said: "When a man prays with the Imaam until he concludes, it is recorded that he prayed the rest of that night." [Masaa'il]]
Abu Hurairah (radiyallaahu`anhu) narrated that the Messenger of Allah Muhammad (sallallaahu`alaihiwasallam) said: "Whoever stands (in qiyaam) in Laylatul-Qadr [and it is facilitated for him] out of faith and expectation (of Allah's reward), will have all of his previous sins forgiven."
[Al-Bukhari and Muslim; the addition "and it is facilitated for him" is recorded by Ahmad from the report of `Ubaadah Bin as-Samit; it means that he is permitted to be among the sincere worshippers during that blessed night.]
It is also recommended to make extensive supplication on this night. 'Aa'ishah (radiallaahu'anha) reported that she asked Allah's Messenger Muhammad (sallallaahu` alaihiwasallam), "O Messenger of Allah! If I knew which night is Laylat ul-Qadr, what should I say during it?" And he instructed her to say: "Allahumma innaka `afuwwun tuh.ibbul `afwa fa`fu `annee - O Allah! You are forgiving, and you love forgiveness. So forgive me." [Recorded by Ahmad, Ibn Majah, and at-Tirmidhi. Verified to be authentic by Al-Albaanee]
Abandoning Worldly Pleasures for the Sake of Worship
It is further recommended to spend more time in worship during the nights on which Laylatul-Qadr is likely to be. This calls for abandoning many worldly pleasures in order to secure the time and thoughts solely for worshipping Allah. `Aa'ishah Bint Abu Bakr (radiallaahu'anha) reported: "When the (last) ten started, the Prophet Muhammad
(sallallaahu`alaihiwasallam) would tighten his Izaar (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-Bukhaaree and Muslim]
And she said: "Allah's Messenger (sallallaahu`alaihiwasallam) used to exert more (in worship) on the last ten than on other nights." [Muslim]