I don't find it difficult, exciting yes, sometimes I can back off a bit but that's my instinct to know when is right and not (only failed me once last year when a gang of young lads were quite threatening, somehow got myself out of that.)
I'm just quite open with the way I work, I don't appear sneaky, I don't skulk off quickly after the shot, I hang around, I remain approachable so if someone does get ansty they can see I'm not shy of showing them who I am too, seems to work. Plus a good old natter and what nots you can soon build up a bit of the 'gift of the gab' and fit in.
For me yes, go a bit unnoticed to start with, get the natural shots sure, but I never leave quickly after.
And if you get caught, I tend to smile at the person and if I get the feeling it's necessaru go up to them and talk, I used to hand out cards with my contact details "Vicky Lamburn - Photographer, sometimes knows what's she's doing" which was a bit of an ice breaker 🙂
I might be there with an ultimate idea in my head but that's the fun of the street, it's the everyday stuff you don't go out hoping to get that gives you a kick when you get the negs/slides in my case.
Vicky