After reviewing a couple entries, it should be emphasized what the article above advised: clip the feathers of only ONE wing on the bird. This imbalances the bird, making it difficult for her/him to fly. If you've clipped BOTH wings on your bird, I wouldn't trust the bird to not eventually...
I'm surprised there aren't more comments about the possibility of bleeding. So here's something from another article: "It is absolutely imperative that you do not cut any new growth feathers with blood in the shaft. You should be able to tell the difference because the shaft will have a pinkish...