These activities are viable for classes of any size.
Questions are the simplest form of interaction and can occur at any time during the lecture.
By asking questions, you not only turn students into active participants, but you can also get a sense of their interest and comprehension. You might try asking questions at strategic points or asking for comments or opinions about the subject. Vary the timing of your questions though to avoid creating a known pattern for students which can lull them into passivity. The Pro and Con Grid lists advantages and disadvantages of any issue and helps students develop analytical and evaluative skills. It also forces students to go beyond their initial reactions, search for at least two sides to the issue, and weigh the value of competing claims.