Effective Language Teaching

The question of effectiveness of language teaching and how to ensure students are actually learning the material can go on forever.  The way that I have successfully learned thus far is through my professors' use of the target language.  Hearing the L2, even if it is just for that short class period, will broaden your vocabulary immensely as long as you are actively listening and participating.  The amount of the language that is not understood may start off as being large, but as each week progresses students will be quicker to pick up on repeated words and phrases and add them to their own personal vocabulary.  Many of the phrases and grammar constructions that I know now and use on a daily basis, I know because of repeating something an instructor of mine has said.  Of course, this is all dependent on what language level you are teaching, a lot of beginning levels will be frustrated and confused if you are rapidly speaking in a language they have never heard before and you will instantly lose their interest.  Once a student has reached an intermediate level or higher, I believe one of the best ways to increase their proficiency is hearing and responding as much as possible in the target language.