Saw it on Metro this morning (I have a flat tire, which compounds my general temporarily-carless malaise by requiring me to take the subway): that lurking rogue, that eldritch horror--the accidentally turned-up suit-jacket collar!
Every time you put your jacket on, reach behind your neck and feel the collar to make sure it's flipped down properly. Do the same whenever you get off the subway--any time I have to use one of the overhead handholds, my collar tends to flip.
Otherwise, you run the risk of having a flipped-up jacket collar during, say, a job interview. (That happened to me once. I've been paranoid ever since.)
It has become trendy to wear an odd jacket with the collar turned up. Some jacket manufacturers even plan for this by using some quirky color of felt under their collars. This is most emphatically not going to cut it in an office setting unless you are The Trendy Guy in your office. Even then, I counsel against it. If, however, you are out at U Street on a Friday night, go nuts.
Further, feel free to wear your overcoat with the collar turned up (while overcoat weather still lasts). This is a common enough look this season that even a well-dressed lawyer can safely pull it off without drawing disapproving glances from his bosses.