Some of the top things to avoid if you want to minimize a larger chest
1) Long necklaces that fall below your bust. When you have a large chest and wear a necklace like this, it just emphasizes your chest, and makes your chest look like a slope that the chain is dangling off of where people can't help but focus on it. Turtlenecks create a similar "slope like" effect.
2) Details and patch pockets on the chest. They just create a focal point where you don't want it, and add extra volume to the chest at the same time.
3) Bulky, over-sized tops and jackets. These are not going to hide your larger chest, they will just make the rest of your upper half look large too.
What to do to flatter a larger chest...
1) Choose a top with V neckline. It brings the eye up, and showing that little extra bit of skin is flattering and elongating (just make sure the "V" isn't too deep...this isn't about showing lots of cleavage).
2) Lower your waist with low slung belts. The illusion of a lower waist creates more space between your full bust and your mid section which will make you look thinner and elongate your entire frame. You can do this by wearing a belt lower on the hips over top of dresses, and tops over jeans.
3) Stick to jackets that are properly tailored and nip in at the waist to add definition between your bust and your midsection.