Two of the most common teaching modes are the lecture and discussion (or variations on those themes). Each of them have advantages and disadvantages (see below) and the trick is to be able to discern which method is most appropriate fo achieving your learning goals.
For a list of the advantages and disadvantages of lectures, see this.
For twenty suggestions for making lectures more participatory, see here.
Research into speech communication also gives insights into the pitfalls that exist in lecturing and how to avoid them.
This site gives some good hints for how to teach large classes.
For information on the advantages and disadvantages of discussions , see this.
It is important that the instructor realize that there are different types of discussions requiring different approaches to succeed. Sequencing questions judiciously and avoiding some of the common errors in questioning will also make your discussions run smoothly and more productively.
The Seminar. What exactly is its purpose? How do you communicate its value to students? How can you run it so that the students get the most out of it? This somewhat idiosyncratic article, written in 1974 by Michael Kahn, provides some thought-provoking ideas on the various forms that seminars take and what we should be seeking when we run a seminar.