We know a lot about best practices with regard to questionnaire design but there is also a lot we don’t know and lots of future research that is needed. Many of the other contributors to this volume are experts in all of these issues and those who know this literature in detail know that everything I will include in this chapter has controversy behind it. There are a limited number of studies on each of these points, we need more, but we need to design questionnaires today and tomorrow and the next day before those studies are done. So taking a look at the literature that exists allows us to reach some conclusions about good ways of designing questionnaires as best we can based on current knowledge, but we need more work in lots of ways.