The first factor to consider is your body frame. If you have a small and slender frame, a large implant may look out of proportion. On the other hand, if you have a larger build, you can usually carry off a larger implant size more easily. Your natural breast tissue also plays a role. If you have more natural breast tissue, you may be able to choose a smaller implant to achieve the desired fullness.

Your lifestyle and activity level are important too. If you're very active and involved in sports or physical activities, a smaller and more stable implant may be more suitable to avoid discomfort and potential complications. For those who prefer a more dramatic look, larger implants might be an option, but it's important to balance aesthetics with practicality.

In terms of shape, round implants are popular for creating a fuller, more youthful look. They are symmetrical and can add volume evenly. Tear-drop shaped implants, also known as anatomical implants, are designed to mimic the natural shape of the breast and can provide a more natural appearance, especially for those with less natural breast tissue.

It's essential to have a detailed discussion with your plastic surgeon. They can use imaging tools and samples to show you how different sizes and shapes will look on your body and help you make the best decision based on your goals and physical characteristics.