How do you come up with sensible financing assumptions during interviews?

Is there a best way of coming up with debt financing assumptions (leverage, junior/senior split, cost of debt, etc.) to use in an LBO? Should I be prepared to talk about how this might differ between industries, size of company, geography, or is it enough to just have roughly [ ]x EBITDA at [ ]% for whatever model I build? 

I feel kind of stupid for not knowing this after two years at a BB but we've always just asked LevFin for inputs and plugged them into our model without any thought. Now that I'm preparing for interviews and looking back at their assumptions, I can't really see why they've used those numbers, or the market has changed so much that I doubt they're realistic anymore.

Thanks in advance