Like Darrenkaye said, if you start off at a very heavy starting point, you could lose 1st in a week, however, if you're say, where I am, you'd lose about half a stone in the first couple of weeks, then dwindle to a couple pounds a week. The lighter you are, the weight comes off slower. There are no 'best' diets. Some people are thriving on SW, I couldn't stand it and have chosen to go onto WW, which is working excellently for me. It's trial and error.
For success stories, I'd suggest going to the success stories forum.