Janice Yalden notes the following principles in designing tasks for language learning/teaching:

Tasks should:

  1. Be realistic;
  2. Have some kind of information gap;
  3. Be unpredictable and free in terms of language and meaning in order to encourage risk-taking, Independence and true language development;
  4. As far as possible meet the learners’ style, needs, expectations and interests.

Based on Yalden (1987) P.152