A visit to the Pine Ridge Reservation  is literally a visit to another country, the reservation is a sovereign nation within the borders of the United States. It is also a place where there are a lot of people willing to share their culture with outsiders.
Attending a powwow is a wonderful way to enjoy Native American culture. It is important to respect the ceremony and the celebration of the tribes and remember that you are a guest. The participants in the dance will be wearing their finest regalia. Honor this and stay away from wearing grungy, torn clothing.
Many powwows, particularly on reservation lands, are held outdoors where there is very little in the way of public seating. Bring lawn chairs or blankets for seating. There are sometimes benches set up around the arena. These benches are reserved for dancers only. Sometimes the areas just behind the benches are reserved for family members so ask before you set up chairs.
Some of the outfits worn by the dancers are breathtakingly beautiful. Remember to ask permission before you take pictures. Listen to the master of ceremonies for cues. Certain songs and ceremonies require the attendees to stand with heads uncovered while they are played. The Grand Entry, Flag Songs, Veteran Songs, and Memorial Songs all require that you stand. Attendees are free to participate in intertribal dances whether wearing regalia or not, but should not try to dance at any other time.
Blanket dances are held at traditional powwows to help defray the costs of the powwows, and to help defray the travel costs of some of the drums. If you see a blanket placed on the grounds and dancers start leaving money on the blanket, feel free to contribute by asking a dancer to place money on the blanket for you. If a dancer drops or loses something off their regalia, particularly an eagle feather, do not pick it up. There are ceremonies for retrieving items that have touched the ground. Ask a dancer or other person in authority for assistance.
It sounds like a lot of rules, but the guiding principle behind attending a powwow is respect. Enjoy the dance, enjoy the food, meet people, and celebrate the beauty of a Native American powwow.