Subway Sketching

I just started sketching people on the subway on my way to work. THe tools are simple just some index cards and a pen or pencil. there are pros and cons to this, the upside is that I get to improve drawing, sketching skills as well as improving my speed. Downside is that some people did not like the idea of someone else drawing them. I remember that this old lady in particular (see below) because she was trying to hide behind her magazine and hat. Of course I stopped drawing her as soon as I realized that that was what she was doing. I carefully choose my subject before drawing mostly I like doing interested faces. Obviously some common sense is needed you know like stay away from people who look like they're having a tough day, chip on thier shoulder, belligerent, angry. And being sensitive to the fact that some people will not want to be drawn .. granted some will say something and others may be too embarrased to do so and will say nothing. Either way if I noticed that they're being discomforted by my sketching them I stop and move on to sketching someone else. So far I haven't had problems yet. Though I wish I realized sooner that the old lady was that discomforted by my sketching to hide under her hat and magazine. Anyways that's life .. one more thing learned. Ok everyone I keep ya'll updated on my sketchings ..though some days will be blanks as I can only sketch when I get a seat on the subway and Provided that I am awake vs. asleep because I have a seat in an airconditioned car.