If you live in one of the big cities likely to be nuked, then it's a good idea to go ahead and start getting really close with family and/or friends who have a nice rural location where you can stay for a while.

Go out of your way to do that, but do not tell them why. They will think you're crazy if you tell them why. Just get as good a contact and friendliness with them as you can, so that you have somewhere to go away from the city once CWII starts.

If you do not have anyone and cannot find anyone who you think would allow you to stay with them, then I'd be getting a helluva nice large tent(or two or three) and all the supplies you need to camp out for a long period of time and then scope out a great rural location where you can camp indefinitely once the SHTF.

Barring that, if you absolutely must stay in the city then it's time to start fortifying your location, preparing your defense, building a blast and fallout shelter(difficult) and gathering up food and supplies.

'Kicking doors' by thugs will be a problem so door reinforcement such as this come in handy - [link to www.amazon.com (secure)]