I know it's been mentioned, but seriously, if the signs say you are to give up certain seats for the elderly or disabled, for the love of little green apples, do it!
Yesterday, an elderly lady using a cane got on the bus. No one moved. (I was already standing.) The driver asked her if she needed a seat, and she said she'd be OK, but she was unsteady on her feet. People ignored her, so the driver called out, "Can this lady get a seat?" Nothing. He said it again, a bit louder. Nothing. The third time, he practically yelled, and I guess people finally figured out that we were not moving until this woman had a seat. I swear!
Also, I don't expect complete silence (although I'd love it), but keep it quiet. At the very least, use your "indoor voice." It's not necessary to scream.
I know the train is loud. I know you like loud music. That still doesn't mean that you should have your iPod so loud that I can identify the song (by an artist I don't like and therefore don't listen to much) bleeding out of your earbuds from 3 rows away.
No, you cannot touch my hair.
I understand that you are going downtown for a fun day/coming home from a fun day/baseball game. That's great. I'm not, so again, please, keep the conversations low and the kiddos in the seats.
If you are traveling with a friend and you plan to speak to them, sit next to them. Don't sit in separate rows and make us all listen to you yelling your conversation. Even worse when 3 people are chatting separated by several rows. Common sense, people!