When I board the bus, the first thing I do after paying and getting my transfer slip is scan the seats. The first group are single seats that ride sideways. These are less comfortable, because your body moves with the bus, and you end up swaying sideways with each lurch.
The second group are two-by-two aisle seats facing forward. If there’s an empty block of two, I grab the one by the window to make room for someone else, but if the bus is basically empty I’ll grab the one by the aisle and put my bag in the other seat.
If it’s crowded, I sit next to a woman (many of whom are reading, and never even glance up).
I NEVER sit next to a man. It sounds absurd and old-fashioned, but it could be misconstrued as interest, particularly if there are other free seats. All the women I’ve seen follow this rule as well; women will sit next to me before they’ll consider sitting next to a dude. And frankly I don’t like it if dude sits next to me, unless there are literally no other seats available. Even then it’s not ideal.