Past tense of 'should' - "I should have", "You shouldn't have", etc.

source: English Lessons with Alex    2010年9月4日
http://www.engvid.com/ The word 'should' doesn't follow the normal rules in English, when used in the past tense. In this grammar lesson, I explain how to use 'should' in the past tense to form sentences like "I should have watched the lesson."