How do the believers (God-fearing people) protect themselves from evil thoughts?

Verses 200-202 of Chapter 7:

And if an evil whisper comes to you from Shaytan, then seek refuge with Allah. Verily, He is All-Hearer, All-Knower. Verily, those who have Taqwa, when an evil thought comes to them from Shaytan, they remember (Allah), and (indeed) they then see (aright). But (as for) their brothers (the devils' brothers) they (the devils) plunge them deeper into error, and they never stop short.

The truth that God alone is the Lord worthy of worship is embedded in every soul!

Verses 172-174 of Chapter 7:

And, (O Prophet,) remind the people of the time, when your Lord brought forth from the loins of the Children of Adam, their descendants and made them bear witness about themselves. He asked them, "Am I not your Lord?" They replied, "Most certainly, Thou alone art our Lord; we bear witness to this. " This We did lest you should say on the Day of Resurrection, "We were unaware of this thing," or lest you should say, "Our forefathers started the practice of shirk before us and we were born after them to their descendants: dost Thou. then, punish us for the sin that was committed by the wrongdoers?" Behold, this is how We make Our Signs clear so that these people return to the right way.

The people who inherited the Holy Book, but used to grab the things of this world without having repentance, had the vain desire to be forgiven by God?

Verse 169 of Chapter 7:

Then after them succeeded an (evil) generation, which inherited the Book, but they chose (for themselves) the goods of this low life saying: "(Everything) will be forgiven to us.'' And if (again) the offer of the like (evil pleasures of this world) came their way, they would (again) seize them (would commit those sins). Was not the covenant of the Book taken from them that they would not say about Allah anything but the truth And they have studied what is in it (the Book). And the home in the Hereafter is better for those who have Taqwa. Do not you then understand.

What induces the believers to admonish those who disobey God?

Verses 163-166 of Chapter 7:

And ask them about the township which was situated on the sea shore. Remind them of what befell its people who used to break the Sabbath (Saturday). Each Sabbath-day the fish appeared in abundance before them on the surface of the water but did not appear at all on other days than Sabbath. This was because We were putting them to test on account of the acts of disobedience they did. Also remind them that when some people from among them asked the others the answer that was given by some of them, "Why do you admonish those people whom Allah is about to destroy or punish severely?" they replied, "We admonish them in order to be able to offer an excuse before your Lord and we also hope that they might refrain from disobedience to Him." However, when they totally forgot the teachings they were reminded of, We saved those who used to forbid evil, and seized with a severe scourge all others who were transgressors, because of the acts of disobedience they did. But when even after this they disdainfully persisted in that from which they were forbidden, We said to them, "Become apes-- despised and disgraced!"

People who have themselves gone astray and misled others as well during the lifetime will receive double torment in hereafter!

Verse 38 of Chapter 7:

(Allah) will say: "Enter you in the company of nations who passed away before you, of men and Jinn, into the Fire.'' Every time a new nation enters, it curses its sister nation (that went before) until they are all together in the Fire. The last of them will say to the first of them: "Our Lord! These misled us, so give them a double torment of the Fire.'' He will say: "For each one there is double (torment), but you know not.''

What are the physical and spiritual conducts enjoined by God during the act of worship?

Verses 29-31 of Chapter 7:

(O Muhammad,) say to them, "My Lord has enjoined justice and righteousness; (He has also enjoined that) you should keep aright your direction during every act of worship and invoke Him alone, dedicating your faith sincerely and exclusively to Him; you shall be created again just as He has created you now. He has shown the Right Way to some but has justly left others to go astray. This is because, instead of Allah, they have made satans their guardians, and yet think that they are on the Right Way." O children of Adam, dress yourselves fully, properly and decently at the time of every worship; eat and drink, but do not transgress, for Allah does not like the transgressors.

Believers always feel that their prayers, sacrifice, living and dying in this world are only for God?

Verse162 of Chapter 6:

Say: "Verily, my Salah, my sacrifice, my living, and my dying are for Allah, the Lord of all that exists.''

God will multiply the reward for a good deed while giving only that much of punishment deserved for an evil deed in Hereafter!

Verse 160 of Chapter 6:

Whoever brings a good deed shall have ten times the like thereof to his credit, and whoever brings an evil deed shall have only the recompense of the like thereof, and they will not be wronged.

People who profess to believe but adopt the way of disobedience, are equivalent to those who do not believe!

Verse 158 of Chapter 6:

Do they then wait for anything other than that the angels should come to them, or that your Lord should come, or that some of the Signs of your Lord should come! The day that some of the signs of your Lord do come, no good will it do to a person to believe then, if he believed not before, nor earned good with his faith. Say: "Wait you! We (too) are waiting."

Based on what characteristics of people does God decide to lead them astray or guide to the straight path?

 

Verses 26-27 of Chapter 2:

Well, Allah is not ashamed to cite the similitude of a gnat or of something even more insignificant than this. As for those who believe, they come to know from the same similitude that it is the Revelation from their Lord; but those who disbelieve, say, "What does Allah mean by such similitudes?"Allah leads astray many and guides many to the right way by the same thing. And He leads astray only those who disobey Allah; who break Allah's covenant after ratifying it; who cut asunder what Allah has ordered to be joined,and who produce chaos on the Earth.These are the people who are indeed the losers.

Verses 15-16 of Chapter 5:

O People of the Scripture! Now has come to you Our Messenger explaining to you much of that which you used to hide from the Scripture and passing over much. Indeed, there has come to you from Allah a light and a plain Book. Wherewith Allah guides all those who seek His Pleasure to ways of peace, and He brings them out of darkness by His permission unto light and guides them to a straight path.

 Verses 125-127 of Chapter 6:

So (the fact is that) whomsoever Allah wills to guide aright, He makes his breast wide open to Islam, and whomsoever He wills to let go astray, He makes his breast narrow and squeezes it so tight that (at the very idea of Islam) he begins to feel as if his soul were climbing up towards the sky. Thus Allah sets the impurity (caused by their deviation from the Way of Islam) over those who do not believe, whereas this Way is the Straight Way of your Lord, and We have made its signs quite clear for those who are amenable to advice. There is an abode of peace or them with their Lord, and He is their Protector because of the good works they are doing. 

Verses 146-147 of Chapter 7:

I shall turn away from My Ayat those who behave arrogantly on the earth, without a right, and (even) if they see all the Ayat, they will not believe in them. And if they see the way of righteousness, they will not adopt it as the way, but if they see the way of error, they will adopt that way, that is because they have rejected Our Ayat and were heedless of them. Those who deny Our Ayat and the meeting in the Hereafter, vain are their deeds. Are they requited with anything except what they used to do.

Do the same revelations of God guide those having knowledge (believers) while mislead the wrongdoers (disbelievers)?

Verses 26-27 of Chapter 2:

Well, Allah is not ashamed to cite the similitude of a gnat or of something even more insignificant than this. As for those who believe, they come to know from the same similitude that it is the Revelation from their Lord; but those who disbelieve, say, "What does Allah mean by such similitudes?"Allah leads astray many and guides many to the right way by the same thing. And He leads astray only those who disobey Allah; who break Allah's covenant after ratifying it; who cut asunder what Allah has ordered to be joined,and who produce chaos on the Earth.These are the people who are indeed the losers.

Verse 105 of Chapter 6:

Thus do We state Our Revelations over and over again indifferent ways so that the disbelievers might say, "You have learned these (not from Allah but) from someone else;" and so that We may make the Reality plain to those who have knowledge.

Verse 82 of Chapter 17:

And We send down in the Qur'an that which is a healing and a mercy to the believers, and it increases the wrongdoers in nothing but loss.

Verse 31 of Chapter 74:

And We have set none but angels as guardians of the Fire, and We have fixed their number only as a trial for the disbelievers, in order that the People of the Scripture may arrive at a certainty and the believers may increase in faith, and that no doubts may be left for the People of the Scripture and the believers, and that those in whose hearts is a disease (of hypocrisy) and the disbelievers may say, "What does Allah intend by this example'' Thus Allah leads astray whom He wills and guides whom He wills. And none can know the hosts of your Lord but He.

Does believing in the Hereafter (Day of Judgement) lead to believing in the Holy Book (Al-Quran) and sincerely following the instructions therein?

Verses 91-92 of Chapter 6:

Those people formed quite a wrong estimate of Allah, when they said, "Allah has not sent down anything to any man." Ask them: "Then who sent down the Book, which Moses brought: which was Light and Guidance for mankind: which you have divided into fragments, a part of which you show to the people and most of it you hide from them: by which you were given that knowledge which neither you nor your forefathers possessed?" -- Just say, "Allah", and then leave them alone to play with their useless arguments. (Like that Book) this is a Book which We have sent down; it is a blessed Book, it confirms that which was sent down before it, and this has been sent down so that you should warn the people of this central place (Makkah) and those who dwell around it. Those, who believe in the Hereafter, believe in this Book, and observe their prescribed Prayers punctually.

How should the believers respond seeing the people engaged in false discourses about Al-Qur'an or deceived by the life of this world?

Verses 68-70 of Chapter 6:

And when you see those who enter into false discourses about Our communications, withdraw from them until they enter into some other discourse, and if the Shaitan causes you to forget, then do not sit after recollection with the unjust people. And nought of the reckoning of their (deeds) shall be against those who guard (against evil), but (theirs) is only to remind, haply they may guard. And leave those who have taken their religion for a play and an idle sport, and whom this world’s life has deceived, and remind (them) thereby lest a soul should be given up to destruction for what it has earned; it shall not have besides Allah any guardian nor an intercessor, and if it should seek to give every compensation, it shall not be accepted from it; these are they who shall be given up to destruction for what they earned; they shall have a drink of boiling water and a painful chastisement because they disbelieved.

At the time of great misfortune the people who set up partners with God call upon Him alone forgetting those partners!

Verses 40-41 of Chapter 6:

Say: "Tell me if Allah's torment comes upon you, or the Hour comes upon you, would you then call upon any one other than Allah (Reply) if you are truthful!'' Nay! To Him alone you call, and, if He willed, He would remove that (distress) for which you call upon Him, and you forget at that time whatever partners you joined with Him (in worship)!

Verse 67 of Chapter 17:

And when harm touches you upon the sea, those that you call upon vanish from you except Him. But when He brings you safe to land, you turn away. And man is ever ungrateful.