A handshake with an open hand origionated, I was told, as a way to show you had no weapons. The idea was to create a form of trust between men during brutal times. Now it seems, according to this video, that dress codes should be implemented to require tucked in shirts and pants that fit.
The high school I went to dropped the dress code right after I graduated because they said it was unconstitutional. But I do remember having to wear clothes without major holes in them that kinda fit at least, shirt tucked in and a belt. Girls had to wear skirts that could be 1" above the knee. Basically you could wear anything you wanted as long as you looked what was reasonably considered acceptable. Of course, being the rebels we were, with few exceptions, we all pushed the limits.