1. The du'a (supplication) is not only worship but it is the brains of worship due to the saying of Allah (swt):

''And your Lord said: ''Invoke Me (and ask Me for anything) I will respond to your (invocation). Verily! Those who scorn My worship [i.e. do not invoke Me, and do not believe in My Oneness] they will surely enter Hell in humiliation!'' [ Ghafir:60]. 

This is similar to the saying of the Messenger (saw):

''The du'a is the brains of worship.'' Reported by at-Tirmizi via Nu'man b. Basheer. At-Tirmizi said the hadith is hasan sahih.

Du'a is worship and Allah loves the servant who supplicates to Him. Du'a is recommended and the one who leaves it has lost much good. If he leaves making du'a due to pride then that person will come under the saying of Allah:

''They will surely enter Hell in humiliation!'' [ Ghafir:60]
I.e. they are humiliated, disgraced and small.

2. Allah (swt) has clarified to us that whilst making du'a we should respond to His command, adhere to the Sharee'ah and follow His Messenger (saw):

''So let them obey Me and believe in Me, so that they may be led aright.'' [ Al-Baqarah:186]
The Messenger (saw) said:

''He supplicates to Allah but his food and drink are of Haraam. So how can his du'a be answered?'' (Reported by Muslim).
The best times in which to make du'a are during the prostration (sujood), in the middle of the night, in the obligatory prayers. Muslim narrates on the authority of Abu Hurayrah (ra) that the Messenger of Allah (saw) said:

''The closest a servant be to his Lord is when he is in sujood (prostration), so make du'a frequently.'' At-Tirmizi reported hadith, which he said is hasan, on the authority of Abu Umaamah
who said: The Messenger (saw) was asked: which du'a is heard most? He replied:

''Du'a in the middle of the night and at the end of the obligatory prayers.'' Also the du'a in the month of Ramadaan carries immense reward. At-Tirmizi reported a hadith, which he said is hasan that the Messenger of Allah (saw) said:

''The supplications of three people are not rejected: the supplication of a fasting person at the time of breaking fast, of a just ruler, and of a person who is wronged. Allah causes their supplications to rise above the clouds, and gates of heaven are opened for them, and Allah says, 'By My Majesty, I will help you, even if it is after a while.'' 

3. The fact that du'a is worship does not mean abandoning the means. The Seerah (biography) of the Messenger of Allah (saw) shows us how he prepared in Badr, arranged the soldiers and placed them in their respective positions. He prepared well for the battle and afterwards he entered the hut beseeching Allah to give victory. He supplicated to the extent that Abu Bakr would say to him:

''Only a part of this du'a is enough (to win) O Messenger of Allah.''
When the Messenger (saw) was given permission to make Hijrah from Makkah to Madinah he utilized all the means at his disposal to succeed whilst making du'a to Allah to keep the Quraysh away from him, to save him from their plots and allow him to reach Madinah safely. So instead of going north towards Madinah he went south and hid in the cave of mount Thawr with Abu Bakr. He used to receive news about Quraysh, about what they were planning through 'Abd ar- Rahman b. Abu Bakr. When he returned to Makkah he made Abu Bakr's son follow behind him to cover the tracks with his cattle in order to fool the Kuffar of Quraysh. He stayed there for three days until the search died down and then he began his journey to Madinah Al-Munawwarah. The Messenger of Allah (saw) did all this while confident that he will reach Madinah safely. Look at how he replied to Abu Bakr when the latter feared Quraysh would find them when he saw them in front of the cave. Abu Bakr said: ''Messenger of Allah, they will see us if they just look down towards their feet.'' The Messenger (saw) replied:

''What Abu Bakr, what do you think about the two with whom the third is Allah?'' He (swt) said:

''For Allah did indeed help him when the disbelievers drove him out, the second of two, when they were in the cave, and
he (SAW) said to his companion (Abu Bakr radhiallahu'anhu): 'Be not sad (or afraid), surely Allah is with us.' [ at-Tawbah:40]
Also he (saw) said to Suraaqah who was on the verge of catching the Messenger (saw) and Abu Bakr in their Hijrah so as to lead Quraysh to them and take the prize, the Messenger (saw) told him:

''Let him return back and he shall have the bangles of Kisraa.''
The Messenger of Allah (saw) used to act upon the means, so that we may emulate him, while at the same time making du'a to Allah to save him from the Qur'aysh's search and foil their plots. When he left his house at night he found his house surrounded by the Kuffar so he threw some dust in their faces.

He was confident that Allah would answer his du'a and save him from them. This is how they were overtaken by sleep while the Messenger (saw) made his way out. Making du'a does not mean we neglect the means but the du'a should be accompanied by the means. The one who wants Islam to be established again should not be happy just to make du'a to achieve it. He must work with those people who are working to establish the Victory and make du'a to Allah for its speedy return. He should beseech Allah in supplication whilst acting according to the means. This is how actions need to be undertaken. He act sincerely for Allah's sake and remain honest to the Messenger and supplicate, imploring Allah in his du'a Indeed Allah is the One Who Hears and Responds to the call.

4. Allah Answers the Du'aa of the one who calls Him. He answers the distressed servant when he calls out to Him. He (swt) said:

''And your Lord said: 'Invoke Me, (and ask Me for anything) I will respond to your (invocation)'. '' [Ghafir:60]

He (swt) said:

''And when My slaves ask you (O Muhammad SAW) concerning Me, then (answer them), I am indeed near (to them by My Knowledge). I respond to the invocations of the supplicant when he calls on Me.'' [ Al-Baqarah:186]
He (swt) said:

''Is not He (better than your gods) Who responds to the distressed one, when he calls Him, and Who removes the evil.''
[ An-Naml:62]

Answering the du'a has a Sharee'ah meaning as clarified by the Messenger of Allah (saw):

''Any Muslim who makes a supplication containing nothing that is sinful and nothing that involves breaking ties of blood relationships, will be given for it by Allah one of these three
things: He may accept his request, or save its reward for him in the next world, or turn away from him an equivalent amount of evil.'' Those who heard it said, ''We would, then, make many supplications.'' The Prophet (saw) replied, ''Allah is more than ready to answer what you ask''
Reported by Ahmad and al-Bukhari in al-Adab al-Mufrad.

He (saw) said:

''The du'a of the servant will be answered if he does not ask for the cutting of blood ties and is not impatient, It was asked: O Messenger of Allah, what is impatience? He said: impatience is when the servant says, 'I supplicated but my du'a was not heard' and so he becomes distressed and leave making supplication.''
Reported by Muslim.

We should make du'a to Allah. If we are honest, sincere and obedient then we can be confident of an answer in the manner shown by the Messenger of Allah (saw). Also, Allah (swt) has ordered us to make Zikr (i.e. remember Allah).
He (swt) said:

'' Therefore remember Me (by praying, glorifying, etc.) I will remember you.'' [ Al-Baqarah:152]
He (swt) said:

''And remember your Lord by your tongue and within yourself, humbly and with fear without loudness in words in the mornings, and in the afternoons and be not of those who are neglectful.'' [ Al-'A'raaf:205]

He (swt) said:

''And remember Allah much, that you may be successful.'' [ Al-Jumu'ah:10]

He (swt) said:

''O you who believe! Remember Allah with much remembrance, And glorify His Praises morning and afternoon [the early morning (Fajr) and 'Asr prayers].'' [ Al-Ahzaab:41-42]

And in the hadith of Abu Hurayrah (ra) who narrated that the Messenger of Allah (saw) said:

''Allah says; 'I am just as My servant believes me to be and I am with him when He remembers Me. So if he remembers Me within himself, I too remember him within Myself. If he remembers Me in a group of people then I remember him in a group that is better than them. If he comes one span nearer to Me then I go one cubit nearer to him; if he comes one cubit nearer to Me then I go a distance of two outstretched arms nearer to him; and if he comes to Me walking then I go to him running.''(This hadeeth is Agreed upon)

Also Muslim reported on the authority of Abu Hurayrah (ra) who said:

The Messenger of Allah (saw) was journeying along the way to Makkah when he (saw) came upon a mountain, which was called Jumdan. He (saw) said that do journey of this Jumdan. The Mufarridoon (people who are alone) have excelled. The Sahabah (ra) asked: O Messenger of Allah (saw) Who are the Mufarridoon? Said: Those men and women who remember Allah very much (all of the time)

Al-Quraafi said in his az-Zakheerah: al-Hasan said: zikr (remembrance) is of two types; the zikr of the tongue which is good, but what is better is the zikr (remembrance) of Allah when He commands you and forbids you.

As for seeking forgiveness it is recommended as well due to the saying of Allah (swt):

''And those who pray and beg Allah's Pardon in the last hours of the night.'' [ Aali 'Imraan:17]

He (swt) said:

''And whoever does evil or wrongs himself but afterwards seeks Allah's Forgiveness, he will find Allah OftForgiving,
Most Merciful.'' [ An-Nisaa:110]

He (swt) said:

''And Allah would not punish them while you (Muhammad SAW) are amongst them, nor will He punish them while they seek (Allah's) Forgiveness.'' [ Al-Anfaal:33]
He (swt) said:

''And those who, when they have committed Fahishah (illegal sexual intercourse etc.) or wronged themselves with evil, remember Allah and ask forgiveness for their sins; - and none can forgive sins but Allah - And do not persist in what (wrong) they have done, while they know.'' [ Aali 'Imraan:135]

Also Muslim reported on the authority of Abu Hurayrah (ra) who said the Messenger (saw) said:

''By the one in whose hand my soul is, if you did not do wrong, Allah Almighty would remove you and bring a people who do wrong and then ask Allah Almighty for forgiveness and He would forgive them.''

At-Tirmizi reported with a hasan isnad on the authority of Anas (ra) that the Messenger of Allah (saw)
said:
''O Son of Adam, as long as you supplicate to Me and have hope in me I will pardon you in spite of what you have done, and I do not care. O Son of Adam, if your sins were so numerous as to reach the lofty regions of the sky, then you asked My forgiveness, I would forgive you, and I do not care. O Son of Adam, if you were to meet Me with enough sins to fill the earth, then you met Me, not associating anything with Me (in worship), I shall greet you with its equivalent in forgiveness.''
Ahmad and al-Haakim reported a hadith by Abu Sa'eed al-Khudri, which the latter graded as sahih and with which az-Zahabi agreed. 

The hadith of Abu Sa'eed al-Khudri states that the Prophet (saw) said:

Iblees said: ''By your Honour I will continue to deceive your servants as long as their souls remain within their bodies. He (swt) will say: By My Glory and My Majesty, I will continue to forgive them as long as they seek my forgiveness.'' 

Ibn Maajah reported with a sound isnad on the authority of 'Abd Allah b. Bisr: I heard the Messenger of Allah (saw) say:

''Blessings are for the one in whose record it is written that he frequently sought forgiveness from Allah.'' 

In a long hadith reported by Muslim on the authority of Abu Zarr that the Messenger of Allah (saw) said narrating from his Lord:

''O my servants. You make mistakes by day and night and I will forgive them all. So seek forgiveness from Me and I will forgive you.''

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