"A keen sense of humor helps to overlook the unbecoming, understand the unconventional, tolerate the unpleasant, overcome the unexpected and outlast the unbearable." 

This quote is one you as an instructor can reflect on as you are conducting your classes.  As a part of our human nature we like to laugh.  Laughter is good for both the body and mind as supported by numerous studies.  As you prepare your lesson plans look for places that you can use humor as a break in the flow in content delivery. With the interjection of humor you are letting the minds of your students rest a bit as they take in the humor you are sharing with them. Also, these "humor" breaks reinforce to your students your human side as they see you as a person that likes to laugh and enjoy being part of their learning process.  You will find that the students will start to bring you examples of humorous things that they have heard or read about in the field once they know you enjoy sharing them.  This becomes a part of rapport development as well.

Use humor wisely.  You never make fun of a student, group of people or any topic that might be perceived as offensive.  Students really like humorous examples of things that have happened in their career field.  So spend a little time thinking through your experiences and jot down those that were humorous to be shared with your students at the appropriate time in the course.  Your purpose in using humor is provide a break, reinforce a point or illustrate to your students different ways of applying the content of the field. 

Use of humor will help you in working through tense situations or discussions in class.  It is amazing how a smile and humorous example can change the atmosphere enough to enable you to maintain control of the situation and keep the class moving forward.