Once in a while there was a rhyme and reason to the process.  On those days the line formed according to who had been there first, courtesy for elderly people, and consideration of minutiae of social status.  Those were odd days.  They weren’t special, like the relaxed and relaxing days Jack enjoyed.  They were just… odd.  On these days it was as if some universal concept of social order and space had propagated to each mind.  
Most often the line seemed to form according to a mix of motivations.  Some individuals would push themselves forward, others would fit in where they could, and certain others would attempt to establish a personal sense of order with their movements.  Usually Jack just fell towards the back, or the very end of the line.  Only on days of extreme agitation would he push himself forward; or on days of extreme self interest, such as when the line was remarkably long and space would be standing room only on the violently rolling bus.
Today was cold, but the line was short, so Jack fell towards the back of the line.  As he stepped, clip clop pace to the double door, a middle-aged black lady approached from opposite the line.  She obviously was not a student, in her elegant black and brown dress, and because she had not attempted to fit into the line.  Jack glanced at her face, smiled very slightly, dipped his head just a bit, and waited for her to enter the bus before him.  For some reason, perhaps because she felt the order of the line to be special and students to be somehow privileged, she stood patiently still while lightly smiling at Jack.  This signaled to Jack that he should enter before her and so he did.
Jack trod the triple steps of the bus entrance.  He glanced up to see who was driving today.  Each driver had a different personality, a different style of driving, a different way of managing the passengers, and Jack had a different way of responding to each.  He frowned just a little, as he recognized the driver he most disliked.  
Today Jack was trying to maintain his calm.  To do so he would have to ignore, avoid, or deal with things disliked and so he gave the driver no more attention than necessary.  He clomb the last step, and stood in front of the metal box where one paid fare.  Glancing at the balding head, the white hair, the red-white skin, the sunglasses, the mustache, and the blue shirt, Jack dropped the two quarters into the machine.  Flattening the dollars, he watched them slide, machinery whirring, into the guts of the bus.  After a last, neutral glance at the driver, he turned and looked at the passengers and seats.
For Jack, choosing a seat on the bus was a simple procedure.  The public transportation buses Jack rode had doors in their middles.  If the seat directly opposite these doors was open, he sat there. 