The better teachers have training, experience, and a resource library of commercial textbooks and other materials.  For beginning students, teachers may use a textbook to provide systematic coverage of grammar and vocabulary.  For intermediate students who want to practice what they already know, teachers may focus on conversation and occasionally send pages from a textbook to work on weak areas.  For intermediate and advanced students who want to learn new skills, teachers may use a textbook or materials from their resource library to help the student reach the next level.

If you are considering teaching, I'd recommend working with a coursebook first to get the hang of it. When you become a more experienced teacher you can teach with "minimal resources".