That's actually a pretty big question. Some people use a number of different scrapers depending on what they are doing. The big paint scrapers with a handle are used for more heavy material removal, card scrapers, knives, scissors and others for more fine work. I made one out of an old 10" circular saw blade, as PatM mentions.
I find card scrapers hard on the fingers because you flex them a bit to curve the edge against the wood. On my saw blade scraper I cut one side with a straight edge and one side with an arc so that it presents to the wood similar to a properly used card scraper, but it is much easier on the fingers because there is no flex required (or possible, it is too thick to bend by hand).
Also, if you haven't got one, get a farrier's rasp for the rough wood removal. Prices are reasonable and they are a fantastic tool for carving down a stave with good control.
Mark