Frequent short quizzes can serve as a useful checkpoint to identify students who need help before their grades are so seriously affected that they simply stop trying or drop the class. Students can also use them to pinpoint which units they need to study or get help with.
Usually, quizzes will be short, timed (10 to 15 minutes) assignments of six to ten multiple-choice or short-answer questions covering the course objectives for a single unit. This helps to ensure that your students cannot skim the reading material or check other sources for the answers. Often, you will want to use question pools so your students cannot share answers.
You should require entire assignment submission and penalize students if they use more than two submissions. You might also want to require students to certify that they completed the work on their own or that they have complied with your school's honor code.
To implement this use case, see the following topics: