I want to lose weight, what should i do?

I'm a girl and i'm 16 years old. I weight 130-145 pounds(forgot what i weighed last time but it was between the two) and i am 5'1''. I want to lose weight fast. I was thinking about doing the isagenix cleanse (which costs a lot of money), the atkins diet or the south beach diet. What should i do? ):