Approaching People to take a photograph has always been a bit awkward to me. It's the anticipation of how they may react. When Dar and I went out we both wanted to be a little more proactive. We asked a few different people through the day. Some said yes and a few said no. No one chased us away with sticks. These fellows were out passing the time enjoying the weather. I asked and they said sure and carried on talking. Dar and I took a few shots then chatted with them for a few minutes. It was a pleasant encounter. Thinking about it,I don't believe there is a special approach or anything. Just ask and if they say no, then don't.
Used the 100mm 1/80th sec f4.5 iso 100