A clean outline stroke makes titles pop, especially when they’re sitting on top of busy footage that would wash them out.
Steps to add stroke around text
Select your text layer and open the Character panel. Set Fill to None (the slash icon) if you want only an outline with no fill.

Enable Stroke, choose a color, then increase the Width until it looks right.

If you want both fill and outline together, simply keep Fill on.

One more thing
Use Layer Styles → Stroke (right-click your text layer) for a layer-style outline. Gives you more control and creative options.
Related how-tos
How to add a new text layer in After Effects
How to make glowing text in After Effects
How to add a shadow in After Effects
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