Assessing students' participation

Monitoring and evaluating students’ performance during classes can be rather complex since many factors are involved. Different aspects should be taken into consideration when assessing participation. What and how to asses participation has been a vocal issue in teaching; some students participate more than others, so is it the Frequency of participation that what teachers should assess? The responses and information given by the students vary considerably, the information sought for may be basic and mere "parroting" or something reflecting thought and intellectual curiosity. We are here considering the quality of participation.
Whatever the method of assessment is teachers should develop strategies that promote students' active involvement in their learning. Follow the link below to read more about strategies used to promote the learners' engagement.
http://www.edutopia.org/project-learning-teaching-strategies

The second concern is how to asses participation, some teachers use checklist,others examine students' notes and set pop up quizzes.
As an educator, how do you deal with assessing and evaluating participation?