Take photos in a sensitive way by being informed of local peoples' attitudes towards being photographed.
Learn about the culture's traditions or superstitions, and always ask for permission, before pressing the shutter.
Money may be expected. Establish a price before you take the photos to avoid unpleasant misunderstandings.
Places of worship, museums, memorials, cemeteries and historical sites may have policies on picture taking which may not be clearly displayed. Always ask the attendant.
Airports, military bases, and government buildings may be interesting to photograph, but are generally off limits. Taking photos in these places may be punished harshly. It is not worth the trouble. Ask first.
Consider if the person being photographed could be put in peril with local authorities in countries that may have sensitive political and religious conditions.
Children are wonderful subjects, but always ask the parents for permission first.