Jeff suggests that we ask questions to nominees on meta with the Election tag.
So far I've seen four ways to ask questions to nominees:
Right in the comments of nominee's introduction.
One question in a meta, every nominee can answer (Jeff's suggestion).
Many questions in a meta post (used on Super User by Ivo Flipse).
One post on meta for many questions. Questions are asked in answers. Nominees edit the answer with their own. (used on Math.SE).
I've used method 2 by grouping two questions with a very similar subjects as per Anna's suggestion.
What's is your preferred way?