Characters
Do not make hands that resemble hot-dogs, but rather human hands.
Do not make characters wear complicated clothing – keep it simple and comfy.
Do not make animal characters with threatening assets – no claws and fangs.
Composition
Do not insist on ideas which consist only of people working in an office. There are more ways to show a person or creature “working”.
Color
Do not step away from the main colors when working for a specific product.
Do not combine low-contrast values next to each other. Feel free to edit the material, if necessary, to achieve this.