Shadow gives depth and makes objects pop off the background — it’s the simplest way to add dimension.
Steps to add drop shadow
Select a layer and go to Effect → Perspective → Drop Shadow.

Adjust Color, Distance, Softness, and Opacity until it looks natural for your scene.

Reposition Direction to match your scene’s light source so the shadow falls the right way.

One more thing
Duplicate the shadow effect for layered, realistic depth — one soft shadow behind a sharper one creates much more believable dimension.
Related how-tos
How to make glowing text in After Effects
How to create a blur effect in After Effects
How to add stroke around text in After Effects
Need more help? Explore all our How-tos in one place.