Mortica_Smith

Tip #1
Do not use solid black for linind unless the main theme of your character is black, even then, try to use a dark grey.

Tip #2
Try to limit your palette to 10 colours or less (not including line art/shades) This draws more attention to the facial features and the whole posture

Tip #3
Expressions can be told through more than just the mouth. With cartoons, try to exaggerate a character.