Starting with simpler, more fundamental questions can motivate a respondent to go further. Aim to balance basic and complicated questions wherever you can. If you begin with basic questions that make the respondents feel comfortable with your survey, you’ll usually find that they fill out all of the answers - even when there are complex questions.
How about kicking off the survey with demographic questions? You can easily ask your respondents' gender survey questions, sex survey questions, race survey questions, or age survey questions.
Don't forget to reserve and make optional delicate questions for the conclusion. If respondents encounter a challenging question right away, they will assume that all of the questions will be equally challenging, making completing the survey seem like rocket science.
However, if they see it near the end, they might make the effort as they are aware that they are almost finished.
Organize related questions together and arrange the questions logically to establish a conversational flow. The survey's tone and voice should also be appropriate given who it is from and who it is intended for.