And you guys think we are juridical?! Don't you have pious customs that developed over time from inspiration that aren't precisely spelled out in council documents or episcopal declarations/pronouncements? As Benedict XVI said in one of his interviews, the Church does not proclaim a bunch of "No"'s, but rather encourages one to say "Yes" to God and experience the freedom that accompanies submitting to God's will (of course, BXVI said it much more eloquently).
The Pharisees followed all the rules (the letter of the law) and Jesus called them whited sepulchers...
Lots, but we do them standing. :)
Bowing and crossing (constantly) are such customs. On the Pentecost we do kneel and during the Great (Holy) Week we prostrate (but not on Sundays).
We have always found a way to accomplish that which was given to us and add our own customs without violating the Tradition.
One such example is the innovation (I believe 5th century) of placing the Body of Christ into the Holy Chalice containing the Precious Blood and for the communicants to receive the Body and the Blood, just as the clergy do.