This paper presents questions within a consideration of the nature of doctoral viva examinations from an international viewpoint. We argue that preparation for the viva should begin early - certainly not just immediately after the thesis submission. Key viva questions can be used in a preparatory process with supervisors over time to develop candidates' thesis thinking and research capability. The paper gives guidance and advice for "candidates" (and for "supervisors" to help candidates) about how to prepare practically for the viva. More importantly this should help them to enter the mindset of examiners. This enables candidates to enter fully into discussion of a thesis confidently and enthusiastically, to share their research thinking in a focussed manner which takes broad issues into account. In a detailed Appendix, we share a repertoire of 60 examples of generic viva questions which are commonly asked in many international contexts, together with guidance about answers in brackets. Using these iteratively with supervisor help, candidates are encouraged to generate their own specific questions as part of a formative research process. Viva preparation guided by key questions can begin early as an inherent part of the research-and-writing process: questions are first "for" candidates, then developed "with" candidates, and then finally in a viva put "to" candidates. The questions are a framework for supervisors, too, who are often examiners themselves.