
(May Peace, Mercy and Blessings of Allah be on all of you)
Lail and Qadr both are Arabic words, means "Night" and "Power / Decree" respectively, so the Laila-tul-Qadr means the "The Night of Power / Decree".
Now Why is it the night of Power / Decree?????
This is a night when the events of coming year are handed over to angels thus, news of death, sustenance, Hajj, rain, disasters etc all are written and handed over to the relevant angels (Tafseer Ibn e Kathir). You can also call it "Night of Destiny" as Allah mentioned about Lailat-ul-Qadr in Quran, (Surah Ad-Dukhan).
Ha, Meem. By the clear Book, Indeed, We sent it down during a blessed night. Indeed, We were to warn [mankind]. On that night is made distinct every precise matter - [Every] matter [proceeding] from Us. Indeed, We were to send [a messenger] As mercy from your Lord. Indeed, He is the Hearing, the Knowing. [Surat 44,Ad-Dukhan (Verses 1-6)].
Quick Understanding Of Lailat-ul-Qadr
This is a blessed night and it is hard to imagine its importance but in short we can make its importance understandable by saying:-
1. All works for the coming year are decided in this night.
2. Qur'an was revealed in this night.
3. Gabriel A.S along with other angels come on this earth in this night by the order of Allah.
4. Worshiping Allah in this night is better than 1000 months i.e. 83.3 years (with respect to reward) as Allah mentioned in Qur'an (Surah Qadr). It means if we pray in this night we are not going to get reward of praying one night only but the reward for praying 1000 months. What could be better then praying one night and getting the highest reward of 1000 months?
Definitely its mercy of Allah to reward like this and to inform us about it. We can pray for our welfare to Allah as the important decisions are being decided and handed over to angels in this night.
Allah told us that there is peace in this whole night until the appearance of Dawn. Here is a brief description from Quran ' Surah Qadr.

1. Verily! We have sent it (this Qur'an) down in the night of Al-Qadr (Decree)2. And what will make you know what the night of Al-Qadr (Decree) is?3. 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, i.e. 83 years and 4 months).4. Therein descend the angels and the Ruh [Jibrael (Gabriel)] by Allah's Permission with all Decrees, 5. Peace! (All the night, there is peace and Goodness from Allah to his believing slaves) until the appearance of dawn. (Surah 97 Al Qadr).
How can we Determine Lailat-ul-Qadr?
As far as determining "Lailat ul Qadr" (the Night of Power /Decree) is concerned, it has been reported to be during one of the odd numbered nights of the last ten odd nights of Ramadan, i.e. 21st, 23rd, 25th, 27th or 29th. So the one who want to be blessed and get the maximum reward; must try to find out this night.
Ibn Umar (Allah be pleased with him) reported Allah's Messenger (may peace be upon him) as saying: He who is anxious to seek it (Lailat-ul-Qadr) should seek it in the last ten (nights of Ramadan). (Muslim , Book 006, Number 2622)
The one who fast for Ramadan and pray out of sincere faith and hope for the best reward from Allah, all his / her previous sins will be forgiven in sha' Allah (if Allah wills).
Narrated by Abu Huraira (Allah be pleased with him) The Prophet (May peace be upon him) said, "Whoever fasted the month of Ramadan out of sincere Faith (i.e. belief) and hoping for a reward from Allah, then all his past sins will be forgiven, and whoever stood for the prayers in the night of Qadr out of sincere Faith and hoping for a reward from Allah, then all his previous sins will be forgiven ." (Bukhari, Volume 3, Book 32, Number 231)
Salim b. 'Abdullah b. 'Umar (Allah be pleased with them) reported that his father said: I heard Allah's Messenger (may peace be upon him) as saying: So far as Lailat-ul-Qadr is concerned, some persons among you have seen it (in a dream) in the first week and some persons among you have been shown that it is in the last week; so seek it in the last ten (nights). (Muslim, Book 006, Number 2620).
It is better if someone can practice Itikaf (to devote ourselves for the sake of Allah's remembrance in Masjid (mosque) and avoid worldly deeds) in the last 10 days of Ramadan as it was practice of our beloved Prophet Mohammad (Peace be upon him).
Narrated by Aisha(Allah be pleased with her): Allah's Apostle used to practice Itikaf in the last ten nights of Ramadan and used to say, "Look for the Night of Qadr in the last ten nights of the month of Ramadan ," (Bukhari Volume 3, Book 32, Number 23)
Ibn Umar (Allah be pleased with him) reported Allah's Messenger (may peace be upon him) as saying: Seek it (Lailat-ul-Qadr) in the last (ten nights).If one among you shows slackness and weakness (in the earlier part of Ramadan), it should not be allowed to prevail upon him in the last week. (Muslim, Book 006, Number 2621).
Prophet Mohammad Peace be upon him asked us to pray as following if we may find Lailat ul Qadr.
Ref of Dua for Lailat-ul-Qadr : "Tirmadhi hadith # 3513 & Ibn e Majah hadith # 3850"
Signs Of Lailatul-Qadr
Abu Huraira (Allah be pleased with him) reported: We were talking about Lailat-ul-Qadr in the presence of the Messenger of Allah (may peace be upon him) and he said: He who amongst you remembers (the night) when the moon arose and it was like a piece of plate (at the fag end of the month in a state of waning). (Muslim, Book 006, Number 2635).
Zirr b. Habaish (Allah be pleased with him) reported: I asked Ubayy b. Ka'b (Allah be pleased with him): Your brother (in faith) Ibn Mas'ud says: He who stands (for the night prayer) throughout the year would find Lailat-ul-Qadr, whereupon he said: May Allah have mercy upon him; (he said these words) with the intention that people might not rely only (on one night), whereas he knew that it (Lailat-ul-Qadr) is in the month of Ramadan and it is the twenty-seventh night. He then took oath (without making any exception, i.e. without saying Insha Allah) that it was the twenty-seventh night. I said to him: Abu Mundhir, on what ground do you say that? Thereupon he said: By the indication or by the sign which the Messenger of Allah (may peace be upon him) gave us, and that is that on that day (the sun) would rise without having any ray in it. (Muslim, Book 006, Number 2633).
'Abdullah b. Unais (Allah be pleased with him) reported Allah's Messenger (may peace be upon him) as saying: I was shown Lailat-ul-Qadr; then I was made to forget it, and saw that I was prostrating in water and clay in the morning of that (night). He (the narrator) said: There was a downpour on the twenty-third night and the Messenger of Allah (may peace be upon him) led us in prayer, and as he went back, there was a trace of water and clay on his forehead and on his nose. He (the narrator) said: 'Abdullah b. Unais used to say that it was the twenty-third (night). (Muslim, Book 006, Number 2631)
Abu Salama (Allah be pleased with her)reported: 'We discussed amongst ourselves Lailat-ul-Qadr. I came to Abu Sa'id al-Khudri (Allah be pleased with him) who was a friend of mine and said to him: Would you not go with us to the garden of date trees? He went out with a cloak over him. I said to him: Did you hear the Messenger of Allah (may peace be upon him) making mention of Lailat-ul-Qadr? He said: Yes, (and added) we were observing i'tikaf with the Messenger of Allah (may peace be upon him) in the middle ten days of Ramadan, and came out on the morning of the twentieth and the Messenger of Allah (may peace be upon him) addressed us and said: I was shown Lailat-ul-Qadr, but I forgot (the exact night) or I was caused to forget it, so seek it in the last ten odd (nights), and I was shown that I was prostrating in water and clay. So he who wanted to observe i'tikaf with the Messenger of Allah (may peace be upon him) should return (to the place of i'tikaf). He (Abu Sa'id al-Khudri) said: And we returned and did not find any patch of cloud in the sky. Then the cloud gathered and there was (so heavy) a downpour that the roof of the mosque which was made of the branches of date-palms began to drip. Then there was prayer and I saw the Messenger of Allah (may peace be upon him) prostrating in water and clay till I saw the traces of clay on his forehead.
(Muslim, Book 006, Number 2628)
Lailat-ul-Qadr Mubarak to all of you. May ALLAH forgive our sins and shower His blessings on us and may He guide us thorough all the life on right path Ameen. Lots of prayers and best wishes for all of you. You are also requested to remember me and my family in your precious prayers please.