As with any form of public transportation, there are many unspoken rules governing personal conduct while on the van. In extreme situations, the rules may be temporarily suspended, but disregard them at your peril.
Rule the First - Let s/he who boards first move to the back. This rule, while ironclad in its simplicity and logic, is most often ignored. By everyone. Rule the First breaks down as soon as the first person on the van picks the best seat, which is ordinarily near the front as these people disembark first. Sneaky.
Rule the Second - Let s/he with the widest ass arrange themselves to occupy the smallest possible area. Speaking as someone with, ahem, ample thighs I am a stringent supporter and follower of this rule. I don't want anyone's chubbles encroaching on my space any more than I seek to encroach.
Rule the Second pt. II - In fact, refrain from touching your riding companions all together. A brush or a nudge is acceptable as you are settling in, but after that, even if you have to contort yourself to the point of physical pain, keep your shit to yourself.
Rule the Third - Hygiene. This cannot be stressed enough. Be advised when riding with international passengers who don't always possess the same fanaticism as their American counterparts with regard to bodily odors, you may be best served to sit in the back- even if it means you get off last. Should someone offer you a breath freshening agent, take it.
Rule the Fourth - If you must use your phone on the van, at least make it interesting for everyone listening. I would much rather hear a profanity laden tirade about alleged public/private indiscretions or even a well thought out treatise on the Electoral College than suffer through another conversational volley about who is going to pick up the kids from day care and wouldn't some overly processed foodstuffs be nice for dinner.
Rule the Fifth - Whilst in the van environment your every sneeze, sniffle, cough, throat clearing, and nose blow is under scrutiny. Everyone gets maybe three of any noise in a given week. Any more than that and I begin to think you not only have a reprehensible lack of social grace but are in fact the second coming of Typhoid Mary.
Learn and live these rules, gentle reader, for they will keep you above reproach, or at the very least, keep you from annoying the hell out of people in an enclosed environment.