I sit down next to the stranger and read a book, except at the moment I don't have anything to read...
I will only stand instead of sitting down if I'm not going very far, but even then you could argue whats the problem sitting next to a stranger for such a brief period of time?
What I don't like, is when people stand near the doors of the buses and trains instead of making room for other people, its okay if you're getting off soon, but all too often people are not.
The trains at perth during peak our are like filled with people, but the idiots are actually just standing in the small 'clearing' like area in front of the doors, when I see this I go straight in, through the group of people, politely requesting they get out of my way, and go down 'isle' of seats to somewhere about the middle and put my stuff down while I stand up.