How do you photograph people (portrait) in their natural environment without affecting or disturbing them?

1) Never select all of the focus points for portraits, pick one.
2) Always focus on the eyes.
3) Shoot wide open for shallow depth of field.
4) Never, ever, shoot a portrait at less than 50mm; try to stay at 70mm or higher.
5) Always shoot in RAW.
6) Always bring a gray card or a piece of a gray card for white balance.
7) Shoot in the shade (Avoid direct sunlight)
8) Shooting carefully on an overcast day.
9) If you must use hot, hard, bright light…
10) Use an existing reflector.
11) Learn the sunny ƒ16 rule.
12) Bring a sheet and a few spring clamps from home.
13) Keep the power-lines and signs out!