I've always considered it to be an example wherein our Lord performed a simple exercise to show His chosen disciples humility, wherein the greater serves the lesser; an example which they were to practice when He would later send them forth to minister to the lost.
Just as Christ Jesus, who was the Greater humbled Himself and became of no reputation by doing that which a servant normally does, then we who choose to lead others must humble ourselves and be as servants to them.
I do NOT think an act of actually washing one another' s feet, although admittedly it is a humbling experience, is an ordinance or ritual which the members of the church are required to perform on either a formal or informal basis. If anything, foot-washing in the churches today is nothing more than following a man-made tradition.
The Lord's Supper is an entirely different matter, for it is a commandment (see
Luke 22:19 &
I Corinthians 11:23-30).