I'm shooting people here in Southeast Asia currently. While in the US, I can be fine with a 55mm or so. However, being in Ho Chi Minh City and Da Nang currently, I'm finding that having a little more stand-off like with a 135mm is giving me better results at least in getting folks to be natural. With the 55mm, people notice you clearly standing there shooting them. See attached, first 3 at 55, last 2 at 135.
When folks notice me pointing at them, I wave and toss a hello there way. If the person catches me beforehand, I'll point at the camera and ask for permission. I'd say about half the time, they nod no and I move on.
Also, on the more candid folks with a bit more cheer in them, I'll step in to them and share the picture. Good laughs or thumbs up usually. No pressure now to have taken a good shot. However, thanks to Facebook, crap shots are acceptable these days.
Next, I'm finding that I get more leeway acting as a friendly photographer that belongs. If I was doing the tourist thing, I don't think I'd get as much access to places or people. As an example, yesterday morning, after the train left, I wanted to catch the cleanup activities. I walked out on the platform and soon had a security dude coming over to send me on. As soon as I lifted the camera and mimed shooting, he went from frowns to smiles and headed back his way. Then, others left me alone as well.
Lastly, I don't look like a bum when shooting. My K-5 II is on a sling, my kit in a belt pack, and I'm wearing long pants and button-down shirts to help give myself more authenticity for being there taking photos.
Anyone have other recommendations on getting noticed, but being able to keep shooting them?