First. Total Depravity refers to the original sin we have all inherited in Adam. Psa. 51:5 , 1 Cor. 15:22 , Eph. 2:1 , Eph. 2:3
Second. Total depravity does not necessarily mean that every man is as evil as he could possibly become, but we are as fallen humans wholly inclined toward evil. We are totally evil, but God in his grace often restrains that evil for his purposes. Ie. The average "nice guy" who just can't bring himself to believe in God, or even someone who appears "good", like Ghandi, etc... James 1:17 -- just as He may also let loose his restraint and raise up a Pharaoh, a Nero Caesar, a Hitler, or an Obama for his purposes, etc... Rom. 9:17 , Rom. 9:18
Third. Total Depravity also may be called "Total Inability". Total Depravity means that no man is able to come to God on his own, apart from God who draws him. Rom. 3:11 , Rom. 3:12 , Isa. 64:6 , Isa. 64:7 , Isa. 64:8 , John 6:44 , John 15:16
The Westminster Confession on this issue is a great read!
Of the Fall of Man, of Sin, and the Punishment thereof
I. Our first parents, being seduced by the subtilty and temptations of Satan, sinned, in eating the forbidden fruit. This their sin, God was pleased, according to His wise and holy counsel, to permit, having purposed to order it to His own glory.[/b]
 GEN 3:13 And the Lord God said unto the woman, What is this that thou hast done? And the woman said, The serpent beguiled me, and I did eat. 2CO 11:3 But I fear, lest by any means, as the serpent beguiled Eve through his subtilty, so your minds should be corrupted from the simplicity that is in Christ.
 ROM 11:32 For God hath concluded them all in unbelief, that he might have mercy upon all.
[b]II. By this sin they fell from their original righteousness and communion, with God, and so became dead in sin, and wholly defiled in all the parts and faculties of soul and body.[/b]
 GEN 3:6 And when the woman saw that the tree was good for food, and that it was pleasant to the eyes, and a tree to be desired to make one wise, she took of the fruit thereof, and did eat, and gave also unto her husband with her; and he did eat. 7 And the eyes of them both were opened, and they knew that they were naked; and they sewed fig leaves together, and made themselves aprons. 8 And they heard the voice of the Lord God walking in the garden in the cool of the day: and Adam and his wife hid themselves from the presence of the Lord God amongst the trees of the garden. ECC 7:29 Lo, this only have I found, that God hath made man upright; but they have sought out many inventions. ROM 3:23 For all have sinned, and come short of the glory of God.
 GEN 2:17 But of the tree of the knowledge of good and evil, thou shalt not eat of it: for in the day that thou eatest thereof thou shalt surely die. EPH 2:1 And you hath he quickened, who were dead in trespasses and sins.
 TIT 1:15 Unto the pure all things are pure: but unto them that are defiled and unbelieving is nothing pure; but even their mind and conscience is defiled. GEN 6:5 And God saw that the wickedness of man was great in the earth, and that every imagination of the thoughts of his heart was only evil continually. JER 17:9 The heart is deceitful above all things, and desperately wicked: who can know it? ROM 3:10 As it is written, There is none righteous, no, not one: 11 There is none that understandeth, there is none that seeketh after God. 12 They are all gone out of the way, they are together become unprofitable; there is none that doeth good, no, not one. 13 Their throat is an open sepulchre; with their tongues they have used deceit; the poison of asps is under their lips: 14 Whose mouth is full of cursing and bitterness: 15 Their feet are swift to shed blood: 16 Destruction and misery are in their ways: 17 And the way of peace have they not known: 18 There is no fear of God before their eyes.
[b]III. They being the root of all mankind, the guilt of this sin was imputed; and the same death in sin, and corrupted nature, conveyed to all their posterity descending from them by ordinary generation.[/b]
 GEN 1:27 So God created man in his own image, in the image of God created he him; male and female created he them. 28 And God blessed them, and God said unto them, Be fruitful, and multiply, and replenish the earth, and subdue it: and have dominion over the fish of the sea, and over the fowl of the air, and over every living thing that moveth upon the earth. 2:10 And a river went out of Eden to water the garden; and from thence it was parted, and became into four heads. 17 But of the tree of the knowledge of good and evil, thou shalt not eat of it: for in the day that thou eatest thereof thou shalt surely die. ACT 17:26 And hath made of one blood all nations of men for to dwell on all the face of the earth, and hath determined the times before appointed, and the bounds of their habitation. ROM 5:12 Wherefore, as by one man sin entered into the world, and death by sin; and so death passed upon all men, for that all have sinned. 15 But not as the offence, so also is the free gift. For if through the offence of one many be dead, much more the grace of God, and the gift by grace, which is by one man, Jesus Christ, hath abounded unto many. 16 And not as it was by one that sinned, so is the gift: for the judgment was by one to condemnation, but the free gift is of many offences unto justification. 17 For if by one man's offence death reigned by one; much more they which receive abundance of grace and of the gift of righteousness shall reign in life by one, Jesus Christ.) 18 Therefore as by the offence of one judgment came upon all men to condemnation; even so by the righteousness of one the free gift came upon all men unto justification of life. 19 For as by one man's disobedience many were made sinners, so by the obedience of one shall many be made righteous. 1CO 15:21 For since by man came death, by man came also the resurrection of the dead. 22 For as in Adam all die, even so in Christ shall all be made alive. 45 And so it is written, The first man Adam was made a living soul; the last Adam was made a quickening spirit. 49 And as we have borne the image of the earthy, we shall also bear the image of the heavenly.
 PSA 51:5 Behold, I was shapen in iniquity; and in sin did my mother conceive me. GEN 5:3 And Adam lived an hundred and thirty years, and begat a son in his own likeness, after his image; and called his name Seth. JOB 14:4 Who can bring a clean thing out of an unclean? not one. 15:14 What is man, that he should be clean? and he which is born of a woman, that he should be righteous?
[b]IV. From this original corruption, whereby we are utterly indisposed, disabled, and made opposite to all good, and wholly inclined to all evil, do proceed all actual transgressions.[/b]
 ROM 5:6 For when we were yet without strength, in due time Christ died for the ungodly. ROM 8:7 Because the carnal mind is enmity against God: for it is not subject to the law of God, neither indeed can be. ROM 7:18 For I know that in me(that is, in my flesh,) dwelleth no good thing: for to will is present with me; but how to perform that which is good I find not. COL 1:21 And you, that were sometime alienated and enemies in your mind by wicked works, yet now hath he reconciled.
 GEN 6:5 And God saw that the wickedness of man was great in the earth, and that every imagination of the thoughts of his heart was only evil continually. 8:21 And the Lord smelled a sweet savour; and the Lord said in his heart, I will not again curse the ground any more for man's sake; for the imagination of man's heart is evil from his youth; neither will I again smite any more every thing living, as I have done. ROM 3:10 As it is written, There is none righteous, no, not one: 11 There is none that understandeth, there is none that seeketh after God. 12 They are all gone out of the way, they are together become unprofitable; there is none that doeth good, no, not one.
 JAM 1:14 But every man is tempted, when he is drawn away of his own lust, and enticed. 15 Then when lust hath conceived, it bringeth forth sin: and sin, when it is finished, bringeth forth death. EPH 2:2 Wherein in time past ye walked according to the course of this world, according to the prince of the power of the air, the spirit that now worketh in the children of disobedience: 3 Among whom also we all had our conversation in times past in the lusts of our flesh, fulfilling the desires of the flesh and of the mind; and were by nature the children of wrath, even as others. MAT 15:19 For out of the heart proceed evil thoughts, murders, adulteries, fornications, thefts, false witness, blasphemies.
[b]V. This corruption of nature, during this life, does remain in those that are regenerated; and although it be, through Christ, pardoned, and mortified; yet both itself, and all the motions thereof, are truly and properly sin.[/b]
 1JO 1:8 If we say that we have no sin, we deceive ourselves, and the truth is not in us. 10 If we say that we have not sinned, we make him a liar, and his word is not in us. ROM 7:14 For we know that the law is spiritual: but I am carnal, sold under sin. 17 Now then it is no more I that do it, but sin that dwelleth in me. 18 For I know that in me(that is, in my flesh,) dwelleth no good thing: for to will is present with me; but how to perform that which is good I find not. 23 But I see another law in my members, warring against the law of my mind, and bringing me into captivity to the law of sin which is in my members. JAM 3:2 For in many things we offend all. If any man offend not in word, the same is a perfect man, and able also to bridle the whole body. PRO 20:9 Who can say, I have made my heart clean, I am pure from my sin? ECC 7:20 For there is not a just man upon earth, that doeth good, and sinneth not.
ROM 7:5 For when we were in the flesh, the motions of sins, which were by the law, did work in our members to bring forth fruit unto death. 7 What shall we say then? Is the law sin? God forbid. Nay, I had not known sin, but by the law: for I had not known lust, except the law had said, Thou shalt not covet. 8 But sin, taking occasion by the commandment, wrought in me all manner of concupiscence. For without the law sin was dead. 25 I thank God through Jesus Christ our Lord. So then with the mind I myself serve the law of God; but with the flesh the law of sin. GAL 5:17 For the flesh lusteth against the Spirit, and the Spirit against the flesh: and these are contrary the one to the other: so that ye cannot do the things that ye would.
[b]VI. Every sin, both original and actual, being a transgression of the righteous law of God, and contrary thereunto, does in its own nature, bring guilt upon the sinner, whereby he is bound over to the wrath of God, and curse of the law, and so made subject to death, with all miseries spiritual, temporal, and eternal.[/b]
 1JO 3:4 Whosoever committeth sin transgresseth also the law: for sin is the transgression of the law.
 ROM 2:15 Which shew the work of the law written in their hearts, their conscience also bearing witness, and their thoughts the mean while accusing or else excusing one another. ROM 3:9 What then? are we better than they? No, in no wise: for we have before proved both Jews and Gentiles, that they are all under sin. 19 Now we know that what things soever the law saith, it saith to them who are under the law: that every mouth may be stopped, and all the world may become guilty before God.
 EPH 2:3 Among whom also we all had our conversation in times past in the lusts of our flesh, fulfilling the desires of the flesh and of the mind; and were by nature the children of wrath, even as others.
 GAL 3:10 For as many as are of the works of the law are under the curse: for it is written, Cursed is every one that continueth not in all things which are written in the book of the law to do them.
 ROM 6:23 For the wages of sin is death; but the gift of God is eternal life through Jesus Christ our Lord.
 EPH 4:18 Having the understanding darkened, being alienated from the life of God through the ignorance that is in them, because of the blindness of their heart.
 ROM 8:20 For the creature was made subject to vanity, not willingly, but by reason of him who hath subjected the same in hope. LAM 3:39 Wherefore doth a living man complain, a man for the punishment of his sins?
 MAT 25:41 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. 2TH 1:9 Who shall be punished with everlasting destruction from the presence of the Lord, and from the glory of his power.