Here are some techniques to help elicit student participation:

• pose questions which invite participation and have more than one right answer
• structure topics and conversations so it is clear where and when to participate
• frame the discussion so that it relates closely to course content
• if the class is large, break students into discussion groups of about 6 to 10 (or even smaller) so that it doesn't seem there is 'nothing new to say' on the topic because 20 people have already answered
• require discussion (class participation) as part of the grade in the course
• early in the course, nag students who don't participate in order to establish active participation behavior
• use discussion regularly throughout the class, not sporadically
• respond to posts in a timely manner to show that student comments are being read, but make sure your comments don't inhibit further student responses
• participation in discussion should be rewarded (give credit for posting) but not graded (grading the quality of each post may discourage participation)
• praise a good response, particularly if it's one you did not anticipate