One way to characterize is for your character to make a plan. The kind of plan the character makes, the level of formality with which it is made, how the character responds when things go according to their plan, how they respond when things do not, what they do when their plan is criticized, who they share their plan with, how their setting influences their plan, how they think about and enact it, and how they revise it, all these things characterize. They also provide a plot.

The plan does not have to be to destroy or save the world. It could be to cross a room for a drink of water, but it ought to be important to your character for reasons your reader can understand.

Try drafting one.