Kol Nidrei is said three times, maybe for emphasis, maybe because this is usual with legal formulas; a medieval work, the Machzor Vitry, says that it shows that at first we are apprehensive about approaching God, but gradually we summon the courage and in the end we face Him, confident that He will forgive.
The reader stands with an elder on each side, forming an ad hoc Beth Din; perhaps the three of them represent Abraham, Isaac and Jacob, for in a sense we call upon our patriarchs to stand by us in our approach to the Almighty.
Kol Nidrei is said standing, out of solemnity and respect. Some say that Satan, the symbolic adversary, says to God at this moment, “I cannot touch them. At this moment they are like angels – unshod, standing, not eating, and without sin.”