There are different shape breast forms. Picking one is a matter of personal preference depending on the look and feel you want.
Asymmetric breast forms are oval with the addition of a narrow tail which points into arm-pit area and come as a left-handed and a right-handed pair. They mimic the shape of genetic ladies' breasts. They are great if you have broader shoulders as they create an illusion of a more natural look.
Triangular breast forms also mimic a genetic breast but with added droop and exaggerated projections for a more supermodel (but less natural) look.
Teardrop-shaped breasts (oval-shaped) can worn in different directions for example horizontal (with the oval pointing towards the arm) or in the direction of the bra strap. The teardrop shape gives a natural look.
For ladies starting or using hormones, the queen enhancer gives a little more bulk to the breast area; you can also use a boob booster or chicken fillets (as they are affectionately known). These can help push up the existing growth to give the impression of a larger breast. These enhancers are also beneficial for someone of a larger form they may be pushed underneath your flesh to push up and expand the look of a natural-looking breast.