I have spent many an hour pondering and planning this (who am I kidding at this point it's probably measured in days). Where I have landed is that with my current family situation, means, and location, significant prepping is not really feasible. So instead where I have focused is on some basic things like keeping enough food and gas on hand at the house at all times for a few days and to be able to drive well out of town should the situation arise, and then the rest of my prep is building as big of a knowledge base as possible.
This has including like knowing driving routes to various locations out of town by memory, learning survival skills like shelter building, trapping, learning a few edible plants in my area, how to make annm/anfo and other usesful items, etc. I figure it costs no money to learn more things, plus it's fun. Then, for things that are absolutely mission critical I have made sure I have hard copies stashed somewhere in case the power goes out and it's too important to risk forgetting. Things like maps and foraging guides.
If you are set on a bunker though, I believe mfbarnes had a pretty nice one
