Street-photography can be on of the most rewarding and the most frustrating things to do.
But the your main weapon is your smile, or/and a friendly face. And when got caught, just explain what you are doing.
It's been said here before; Know your gear, and look confident. And a small rangefinder is less intrusive and intimidating then a Nikon D3 with a tele. The reactions will be accordant most of the time.