Use chance (for example, roll a dice or use playing cards) to determine the order in which students will undertake an activity. Can also be used to call on a students individually.
It makes the process of going around the classroom more interesting. It can help the students to keep more focus.
For example, with small classes students could take turns speaking on a topic. Rather than going around the class in turn it is more engaging to select the order randomly. This can be extended by also randomly choosing a student to summarise what each speaker has said. Since there is no set order students have more incentive to pay attention.
When selecting a student randomly there are two choices. One is to select from the total number of students each time. The other is to choose from the students who have not yet had a turn. It is possible to combine both methods. For example, all students could give a one minute presentation on a topic. The order would be decided randomly but each student would only give a talk once. After each presentation a student could be asked to give a summary. The student to summarise could be chosen randomly from the the whole group (excluding the presenter). This could mean that one student may end up giving more than one summary if chance so dictated. In a single class some students may end up doing more but over time chance should even this out.
Consider including the teacher when making a random selection.