If you want to be slim and toned like Jessica Biel, do cardio and weight training alternatively.

If you want to be skinny like most taiwanese girls with no muscle, starve!

Actually, what you really need is a balanced diet and very good self discipline. In order to lose weight, calories out must exceed calories in. Stay away from oily/fried stuff and eat more protein such as eggs and chicken breast (low calories but high satiety)

My personal opinion is exercise + diet is the best way to lose weight and achieve a nice body. Some people don't look good even though they're skinny cause there's no muscle tone, they don't exercise at all.