For corsages, it is customary to place them on the left side of the dress or on the left wrist of the person wearing it. For boutonnieres, they should be placed on the left lapel of a suit jacket, on top of the lapel and angled in the same direction as the lapel. If someone else is pinning the boutonniere, it should be placed to the right of the tie. It is important to ensure that the boutonniere is secure and straight, and that the needle is not visible from the front. Additional pins can be added for extra security and stability, especially if the boutonniere is large or top-heavy.