Summary: The main difference in how a man stands, when he stands before God, is whether or not he stands with humility or arrogance.
He also told this parable to some who trusted in themselves that they were righteous and regarded others with contempt: “Two men went up to the temple to pray, one a Pharisee and the other a tax collector. The Pharisee, standing by himself, was praying thus, ‘God, I thank you that I am not like other people: thieves, rogues, adulterers, or even like this tax collector. I fast twice a week; I give a tenth of all my income.’ But the tax collector, standing far off, would not even look up to heaven, but was beating his breast and saying, ‘God, be merciful to me, a sinner!’ I tell you, this man went down to his home justified rather than the other; for all who exalt themselves will be humbled, but all who humble themselves will be exalted.”
Two men went to worship; one was accepted, and one rejected. The one was a Pharisee, a very religious person, pillar of the community; the other was a Publican, the town tax collector, certainly not the most popular guy on the block.
Publicans were Jews, but they were unacceptable to their own people, because they worked for the Roman government taking an exorbitant tax (and even more) from their Jewish brothers. The Publican was a despised "Benedict Arnold!" The Pharisees were the respected religious stars of the day.
The story’s conclusion should have been a slam-dunk for the listeners – the religious guy wins, hands down! But Jesus’ punch-line pulled a switch…the tax collector is the one who winds-up right with God, and the church elder becomes the bad guy. What gives here?
Notice, please, the similarities and differences in worship between a religious man, and a renegade; the renegade had humility, the religious man had an “I” Problem.
They Both Stood
Both the Pharisee and the Tax Collector "stood." The difference is in the meaning of the word. In the case of the Pharisee (v.11), the word carries a connotation of confidence. It is the picture of a man standing erect, without any fear.
The Tax Collector also stood; his word meaning, "just barely there." The Tax man was slumped over, hardly daring to lift his eyes heavenward.
So, the main difference in how a man stands, when he stands before God, is whether or not he stands with humility or arrogance. Multiple times Scripture reminds us that “God opposes the proud, but gives grace to the humble.” 
They Both Prayed
Once again the difference between two men was attitude. The Publican asked for mercy, while the Pharisee was there to inform all within earshot (including God) just how good he really was.
Both men told God who and what they are – and they were both right! The Publican told the Lord he was a sinner; he asked for mercy. In the language of the New Testament, the man actually said he was the sinner. This was the attitude of Paul:
This is a faithful saying, and worthy of all acceptation, that Christ Jesus came into the world to save sinners; of whom I am chief. 1 Timothy 1:15
The Pharisee, on the other hand, simply told God that he was good and didn’t need mercy. He listed all the wonderful things he did, and thanked God he wasn’t like ordinary men, especially the tax collector. His prayer was an infomercial for God to watch; God was supposed to be impressed with this good man’s goodness.