Look for places where they hesitate or make mistakes, such as the example below.
This is an indication that the survey questions and layout are not clear enough and need to be improved. Once all the testers have completed the survey review your notes from each session.
At this point it’s normally clear what the major problems are so you can go about improving the survey to address those problems. However, if major changes are needed to the questions or structure it might be necessary to repeat the pretesting exercise with different people before starting the survey.
For example, lack of staff training, challenges with the logistics of distributing and collecting the survey, or errors in data entry.
These can then be fixed before you do the actual survey.