Ask 1 question at a time. For example, do not mix speaker feedback with questions about venue stage.
Avoid bias and complexity in question wording. Group “easy” questions up front and ask for specifics further into the survey.
Only ask questions will impact future decisions for the event. For example in the question “Which, if any, of the following would prevent you from attending a future DevOpsDays Chicago? (Check all that apply)” we do not ask if participants would want sponsor talks because it is not something organizers would change.
(opinion) Force participants to decide. On a scale rating (“For the sponsorship process, how satisfied were you with”) offer 5 to 7 responses so participants
More on survey design from Pew Research, Harvard Business Review and Qualtrics