There's a broad range of render styles, there's no right or wrong about which you should use!
Each type of art render style has their own artistic qualities, strengths and weaknesses which ultimately lends to the type of art piece you want to create. Each style also can also suit a certain type of audience, or message.
Main Points
Compressed range
Key weighted
Cel shading
Wrapped light
Minimal
Under Rendered
Hybrid Cel Shading
Questions to ask yourself
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How can the render style support the idea?
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What forms are a priority for this style?
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Do details closer to light have less definition?
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Do shadows follow the angle of the light?
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Does each light source differ in temperature?