Well, I can only speak on the Eastern Orthodox Christian perspective.
For the true Christian, all of life is a struggle in which, if you are acting in cooperation with the Grace of God, one is continually being sanctified. In other words, there is no line in the sand in this life where one can say 'at this point, I was not saved, and at this point, I am saved.' All of life, one is continually being saved through detaching the nous (the spiritual intellect) from all but God, who is Love.
So, the discernable difference between those being sanctified and those not is that those who are being sanctified are living a life of continual repentance. The true Christian must do everything he can in order to see within himself the potential for every evil, and then repent of it with all his might by relying totally on the Grace of God to keep him from falling into sin.
This is where the parable of the sheep and goats comes in. Those who truly see within themselves the potential for any and every sin, and who rely totally on God to be rescued from these things, they will consider themselves unworthy of Heaven, being so aware of their sins. These sheep will be recognized by their humility.
The goats, however, who think that correct theology, or great wisdom, or feats of asceticism, or hyper-religiosity, or some heartfelt confession of faith, etc. etc. etc., will save them, their arrogance and pride in thinking some endeaver of their own working could act as a means of justification to get them into heaven, these will be exposed as the goats. To take this further, anyone who tries to justify himself in any manner so as to not have to deal with his own defects and sinful tendancies is a victim of pride, and, thus, a goat, even if this means denying the existance of good and evil all-together.