Task-based learning (TBL) is typically based on three
stages.
The first of these is the pre-task stage, during which the teacher introduces and defines the topic and the learners engage in activities that either help them to recall words and phrases that will be useful during the performance of the main task or to learn new words and phrases that are essential to the task. This stage is followed by what Willis calls the "task cycle". Here the learners perform the task (typically a reading or listening exercise or a problem-solving exercise) in pairs or small groups. They then prepare a report for the whole class on how they did the task and what conclusions they reached. Finally, they present their
findings to the class in spoken or written form.
The final stage is the language focus stage, during which specific language features from the task and highlighted and worked on.
Feedback on the learners’ performance at the reporting stage may also be appropriate at this point.
reference:
http://www.prospective.com.mx/english/quees/task.pdf