Teaching is a dialogue, a two-way communication. The teacher's primary function is to provide feedback for the student. Other processes--imparting information, developing curriculum, demonstrating work flow and technique--can be accomplished with one-way communication (books and other media). This doesn't mean a teacher serves only as a sounding board. Effective teachers must constantly adapt and tailor content to suit the particular individuals present during a given instructional session. Through casual assessment, the teacher can determine why or how a student does not understand, and offer an alternative explanation or additional information on the spot. A good teacher also understands the scope and sequence of presentation and sets an appropriate learning pace. Perhaps most importantly, the best teachers provide encouragement for her students.
My teaching style developed from years of instrumental music instruction (string pedagogy), which requires that students actively demonstrate their understanding by doing. I employ this process when I teach information literacy, circulating throughout the computer lab monitoring student performance in real time.
Two additional principles guide my teaching: go from the known to the unknown (always determine first what students already understand) and divide and conquer (divide tasks into discrete steps while remaining aware of the broader goal).
Did I mention I'm a music teacher? I am!