I am finally getting a little bolder about opening my sketch book and recording a few things (as discretely as possible) while I wait at various places.  We did a lot of  'hurry up and wait' at the different airports on our recent trip to India and this time I kept my sketch book handy. But, I discovered that I need to learn to 'speed sketch' so that I may quickly capture people on paper as they don't stay still long enough for my skill level!  Of course, I pretend to be thinking and writing in a journal as I try hard not to appear to stare at anyone.   So, I only used an ink pen to draw and that also meant I couldn't erase and had to live with any and all lines that I put down. 
As I keep a sketch book more regularly and diligently, I am trying to decide if I want to record ideas and not worry about how my drawings look like or work on renderings that are presentable. I have been spending a lot of time browsing Urban sketchers looking at how artists around the world do it. 
Or, I should  just get over myself, not worry about the end result and enjoy the process.