Make no mistake of it, when we die we will go either to Heaven or to Hell. Since our authority for the existence of Heaven also tells us there is a Hell, then if Heaven is real, then so is Hell. We are told by Jesus in Matthew 25:41 that the eternal fire was originally prepared for the devil and his angels.  But the devil and his angels will not be the only ones there.

In Matthew 7:21-23 Jesus states that not everyone that claims to be representing or working for Him, even doing mighty works in His name, will enter the Kingdom of Heaven.  Only those that do the will of His Father will be accepted and the disobedient will be cast out.  Another group that will be in Hell will be those who are neglectful.  In Hebrew 2:1-3 we are told to give heed to the word lest we drift away,  "For if the word spoken through angels proved steadfast, and every transgression and disobedience received a just recompense of reward; how shall we escape, if we neglect so great a salvation?"
Next will be those who sin willfully after receiving the knowledge of truth for all that remains for them is a fearful expectation of judgment and a fierceness of fire which shall devour the adversaries (Hebrews 10:26-27).  Closely related to this group will be those who fall away from the truth.  Peter tells us (2 Peter 2:20-22) that after escaping the defilements of the world through the knowledge of Jesus and then becoming entangled and overcome, then the last state is worse for us than the first.
In James 5:19-20 we are also told that if any among us err from the truth, and one converts him, he shall save a soul from death.  Additionally, Paul tells us in 2 Thessalonians 1:7-9 that those that know not God and to them that obey not the gospel shall suffer punishment, even eternal destruction from the face of the Lord. 
Finally, John in Revelation 21:8 identifies that "the fearful, and unbelieving, and abominable, and murders, and fornicators, and sorcerers, and idolaters, and all liars, shall have their part in the lake that burneth with fire and brimstone; which is the second death." The only way to avoid this second death is to become knowledgeable of God's word. 2 Timothy 3:16-17 states that "Every scripture inspired of God is also profitable for teaching, for reproof, for correction, for instruction which is in righteousness. That the man of God may be complete, furnished completely unto every good work."  However, we must be doers of the word, and not hearers only or we will just be deluding ourselves (James 1:22).
Charles Royal
Decatur AL

"Then shall he say also unto them on the left hand, Depart from me, ye cursed, into everlasting fire, prepared for the devil and his angels:"

"Not every one that saith unto me, Lord, Lord, shall enter into the kingdom of heaven; but he that doeth the will of my Father which is in heaven." "Many will say to me in that day, Lord, Lord, have we not prophesied in thy name? and in thy name have cast out devils? and in thy name done many wonderful works?" "And then will I profess unto them, I never knew you: depart from me, ye that work iniquity."

"For if we sin wilfully after that we have received the knowledge of the truth, there remaineth no more sacrifice for sins," "But a certain fearful looking for of judgment and fiery indignation, which shall devour the adversaries."

"For if after they have escaped the pollutions of the world through the knowledge of the Lord and Saviour Jesus Christ, they are again entangled therein, and overcome, the latter end is worse with them than the beginning." "For it had been better for them not to have known the way of righteousness, than, after they have known it, to turn from the holy commandment delivered unto them." "But it is happened unto them according to the true proverb, The dog is turned to his own vomit again; and the sow that was washed to her wallowing in the mire."

"Brethren, if any of you do err from the truth, and one convert him;" "Let him know, that he which converteth the sinner from the error of his way shall save a soul from death, and shall hide a multitude of sins."

"And to you who are troubled rest with us, when the Lord Jesus shall be revealed from heaven with his mighty angels," "In flaming fire taking vengeance on them that know not God, and that obey not the gospel of our Lord Jesus Christ:" "Who shall be punished with everlasting destruction from the presence of the Lord, and from the glory of his power;"

"But be ye doers of the word, and not hearers only, deceiving your own selves."