The classroom based courses that I enjoyed the most were those that established clear objective for each lesson and where the instructor worked to meet those specific objective during each class. As a learner I enjoyed those classes where there were more interactive discussions annd where the teacher used more resources for explaining the lesson.
The great teachers that I had those who were able to create interest and keep everyone involved. These two can be achieved by making the session an interactive one. Teacher should be well planned and should have a grip on the subject. A good teaher is patient and has genuine interest in the welfare of student.
If I recall two things that were predominant in making lectures which I attended memorable , first the ability of the teacher to keep everyone locked in the discussion .Second perceived value addition at each step of lecture and finally a touch of humor to keep the conversation alive.
Few characteristics which improve class atmosphere and makes learning easy include soothing colour of the walls , absence of outside and inside disturbances like noisy heating or airconditioning system. Distractive colour scheme and uncomfortable furniture can influence learning in a negative way.
And for me a good teacher read and prepare herself sufficiently for every lesson to consolidate subject matter.