Quote Originally Posted by andrewkirkby View Post
A) small camera
B) don't think about what people think.
Funny you should say that.. I find that when I walk around with my battered old Rolleiflex (not a small camera) people don't seem to mind.. in fact they often stop me and ask if they can look at the camera and are more than happy for me to take their picture. I think the eye contact helps and its easy to discretely shoot a frame without even being noticed.

Otherwise I use a very battered Leica M3 and shoot quickly. I try to pre focus so the camera is at my eye for no more than a second or two. Again, I find eye contact helps.. and if the person looks like they really don't want to have their picture taken then I just smile and move on.