The STEAL writing method is a technique used to develop characters indirectly, showing their personalities through their:

Speech: What they say and how they say it
Thoughts: What they think and believe
Effect on others: How other characters react to them
Actions: What they do
Looks: Their appearance and body language

Simple Example

Direct Characterization: “John was nervous”

Indirect Characterization:

John fidgeted with his tie (Actions), his voice cracking as he stammered,
“I-I’m ready for the presentation.” (Speech)

The audience exchanged worried glances (Effect on others).

John managed a sly grin and thought to himself, “You got this ole boy. Can’t fail me now!” (Thoughts)

He slowly took his grimy hands out of his pockets and took the microphone. (Looks)