“When you split wari-bashi, don’t put wari-bashi vertically straight up and break the to the side way. This remains the food for dead people. Put Wari-Bashi horizontal and break them up and down. Also, don’t scrape them after you break them. It is BAD manner to do it.
After finish eating, don’t bend them. Put them back into the paper case to hide only the top of chop-sticks.”
http://www.mustlovejapan.com/manner/waribashi.html

I think that’s reasonable.. after watched this video )