Each CLS instructor will include in the course syllabus information about his or her attendance policy. Generally speaking, we expect you to attend as scheduled.
Every class meeting is important.
The faculty for your non-CLS courses should do include their attendance policies in their syllabi, too. If they don't, it's a good idea to ask. You may think that the instructor doesn't care whether you attend class or not, and then find out that it's an important part of your grade.