The key to TESOL teaching is engaging your students. In contrast to other subjects like math, history or science, learning a language requires a great deal of memorization and habit development. This means that lecturing is simply out of the question. There are more effective ways to teach TESOL.

Young Learners
The trick with kids is games. Lots of games. As you move up the age range and English proficiency spectrum, you can introduce more and more complexity, but with the youngest kids, you need to keep it simple. Don't worry too much about sentence structure, but rather focus on basic vocabulary -- for example, throw some flashcards on the floor and get two students to race to get one and give it to you. Once they have the hang of that, have the winning student take your place -- making it a speaking and listening game, and you can take a break.

If the students are getting bored, introduce a change. It doesn't need to be big by any means, simply a different physical movement. Instead of giving you a flashcard, have them sit on one, have them hold one up or have them clap then jump on it. The tiniest change makes it a new game and completely re-engages your students.

Older Learners
Older students also need to be engaged with their material but often are reluctant to run around and jump and play games. Rather, they are more inclined toward functional, conversational English.

What they need more than anything else is practice, so, again, don't lecture. Focus on topics that they will actually find useful, and encourage a lot of pair and group work. While it can feel like you're not doing anything, older students actually learn far more from listening and speaking to one another than they do listening and speaking to you. After all, if they're in pairs, every single person in the class is either listening or speaking. If you're calling on students and asking questions, only one student is actually engaged. Everyone else is fairly passive.