Standing up is best. on wood or something to cusion the edge from chipping. wrapped with heavy paper with news print between the panes is good. Standing is advised as it is safer for the glass to pick it up and handle in a vertical position. the edges need to be protected from chips, ect, repeat, the edges need to be protected. But glass is stronger than you would believe.

"It ain't a truck if you can't hose out the cab."