Exercising specific body parts does not reduce fat stores in those areas. For example, more situps will not reduce belly fat. Proper nutrition—reducing all around calories—and full-body cardiovascular and resistance (weight-bearing) exercises to burn stored fat is the best general prescription for fat loss. However, spot training certain muscle groups can make them stronger and better toned. Read the discussion at this link for good exercises in the gynoid region (hips/thighs/buttocks).