Serious question: Have you had any bad experiences taking pictures of people working? I imagine that some workers might object..
A presumption of "bad experience"? That speaks volumes. My easy answer is that if you're afraid of people or don't get along easily, don't take pictures of people. Get a good macro and live among the flowers.
With all the snappers around, this world is growing more photo resistant by the day. I'm going to do a separate post about that with a photo from last weekend. Anyway, working people, at least in this country in my experience are so badly treated and regarded, they generally fear what pictures will probably mean. They presume it can't be good. Is it someone who's going to call their company and complain? Has the boss sent someone out to document what they're doing, or not doing? Is it union related -- for or against? Is it OSHA or some other meddling government agency threatening their job? Is it a reporter putting their picture in the paper or on the Internet? Did a lawyer send them out related to some court case? They've got enough to worry about already and mostly just want to do their work and go home and have a beer. So, naturally, they're going to be curious. It's only going to be trouble if you as a photographer make trouble.
I always start shooting unannounced. Eventually someone in the work group will approach me, and I'm glad to talk. I want to alleviate any fear and put them at ease. That's why I always carry my "Who the hell are you?" card -- what people in the commercial world call a "business card." Like arjay, I offer to send them pictures, and my photo site is listed on the card so they can go look at the pictures if they like. That keeps things calm, and they can work and I can take pictures. In some instances you get to meet really interesting people.
There was a guy working on high-voltage power lines nearby. His home was several states from here, and he was working 12-hour days, six days a week. He was living here in an RV, and he owned a plane he used to take himself home on his day off. A railroad runs past my home, and I always go out to take pictures of the train going by. My main interest is the boxcar graffiti. After a year or so, the guys running the train stopped one day, got out of the train and asked why I was always taking pictures. They were really nice guys, just curious. When I told them it was for the graffiti, they said, "Oh, we'll have to find you some better boxes."
Here's a bus driver. He asked me to take his picture as I was getting on the bus. One of my first with the Sigma 35 Art [f/2.8, 1/125 @ ISO 100 on 5D3] in April 2012.