While attending U of A, I noticed how one of my best friends used two straws with his drink at Carl's Jr. When I remarked on this, he told me that it was simply more efficient to drink this way. From that time on I've grabbed two straws.
It seems to me that these tiny things, these little behaviors we all pick up add more depth to a character than any kind of physical description. Too often everything is just sight, or even sound or smell, but those don't add the right kind of depth. Having a character whose default fast food is a gyro or one who emulates a magic show he saw as a kid or one who names his horse after a hockey team are little touches I think add much more to my characters.