In all the talk about photographing street people, no one except Charlie D. has mentioned this yet, so perhaps it's not as well-known a trick as I thought: you take the picture first and then ask permission. If permission is granted, you take a few more (especially with digital, what can it hurt? And you might get a good one). If permission is refused, you can politely refrain...from taking any more. You still have your candid in the camera, you might say.
I think this is justified because 1) it's true that you won't get the same shot after you approach someone (they can become self-conscious or just change position), 2) many people don't realize for sure if you've taken any pictures or not anyway, and 3) people mainly just like being asked.
Posted by: MIKE JOHNSTON