Start with the end objective in mind. You can divide the questionnaire into four sections like. pre interview (access to vaccany information, at portal, company website ad etc, clear job description and eligibility) at interview (convenience of place, time, various forms and information asked from candiates, feedback on secuirty, reception, time taken in attending the candidate, information shared in case of delay and total time taken for whole process, number of interview rounds, follow- up) than at interview (how were was the panel treated them, how were the questions, who were thier queries answered etc) Lastly Post interview, (Time between joining and intiatil induction) how was offer, negotiation, joining time , documnets required were informed. How was induction day. Was the work, desk, mail id all infrstruture required was made avialble etc. How they felt on company culture, policies, communication, matching of job profile with actual work etc.
Suggest you make the intial draft and than ask for feedback form you older colleagues in office. Please make sure the questinnaire is not very cumbersome.