...is a bit like skiing. You have to be aware of your center of gravity, keep your knees bent and over your toes, and keep your body relaxed. When the train is braking or accelerating, lean in the opposite direction (well, that part you don't do when you're skiing). When traveling with Romans early in the morning, there's a delicate dance...learn to move out of the way when a person readies himself for the next stop and says, "Permesso". Do likewise and get yourself ready for the next stop by saying, "Permesso". People are quite respectful.
Later during the day, with other tourists who are clueless as to the rules of the delicate dance...then you say more bluntly and forcefully..."Scusi" to those hogging the door and refuse to get out of your way. And look up at the ceiling or TV monitor or Metro diagram so as not to be forced to look at various body parts exposed.
And when riding the Metro at the end of the day with handbag and various street vendors, be aware of how much room they occupy.
The Red Line has gotten some nice new trains. When we were here a year-and-a-half ago, all the trains were spray-painted over so that when you were inside a car, it was dark and depressing.