Zuko has taught before. He tries to remember that as he guides Katara through her first lesson with little success. He has taught before. But never firebending, and never Katara.
Focus on your breathing. Time each motion with your breath and the flames will respond.
After repeating the same advice twelve times, he decides to try Uncle's method instead.
"Teabending is like fire brewing."
Katara stares.
"I mean—firebending is like brewing tea."
"Am I supposed to know what that means?"
Zuko's face warms. "Never mind. Maybe we'll just do some breathing exercises and try the forms again this afternoon."