Know that your current body shape can be modified somewhat by diet and exercise. Your genetics do determine how body fat is carried on the body; this predisposition cannot be altered. However, if you are not carrying around excessive weight, your body type will not be quite as exaggerated or obvious. Slender women look more similar to each other than obese women.
You cannot "Spot Reduce". Toning a certain body part is possible--you can do core exercises to help flatten abdominal muscles . But your body will not do it in just one place. On women, when women lose weight the change is most dramatic around your chest, hips, and posterior whether you want to or not.
You cannot "Spot Increase". Likewise, short of surgery, you cannot increase parts of your body. Doing chest exercises or using skin creams will not make your bust larger. While chest exercises firm and tone up the bust line, this is not quite the same as increasing your bust.
Certain body types have a predisposition to gain or lose weight in certain areas. For example, a woman with an hourglass figure will tend to gain or lose weight in the bust and hips, and not the waist. But a woman with an apple shape will tend to gain in the hips, and not so much in the bust--even if it is the same amount of body weight.
Cardio and resistance training are most commonly used to alter body types. By knowing if you retain fat more or lose it quicker, you can create an exercise plan to cater to your bodily needs.
What is the ideal body type changes through history. In America during the Victorian period, the "Hourglass" was perfection, and required women to don corsets to get that look. In the 1920s, the ideal woman's body was the boyish "Rectangular" type requiring women to wear girdles and flattening larger chests.
Different cultures and subcultures see different body types as ideal. An African-American woman in America may be praised for a shapely, round posterior. However, the same quality in a woman in Japan may not be.
Remember that dresses are meant to flatter your body, not your body to flatter your dresses. Actresses, models, and the like dress to look wonderful no matter what the underlying body type is. In fact, models do not necessarily look good in everything. When a designer is putting together a photo shoot or runway show, they pick the model that best shows off the clothes...models are not interchangeable.