There is little or nothing to do, bar getting to know a bit of science if you're lacking in that department.
You won't be able to hide young men or adolescent boys, unless you have the ability to send them abroad (which, if war broke out, you wouldn't be able to - they'd have to be out of the country already by that point). But I doubt foot soldiers are a big thing in an age of drones anyway.
Modern wars will be fought with technology. I have always said if I wanted to bring a country to its knees I'd attack the power grid first. Without access to electricity, we're nothing - we've become far too reliant on technology and cities especially would fall into chaos. That attack could be digital or with a few strategically targeted bombs. Anyone who can rub a few brain cells together would also already have placed a few strategic moles in power plants, major banking facilities and digital communication, possibly even fresh water supply. It would only take a few major outages and we're done.
As for stockpiling, no point. Anyone who stockpiles paints a huge target onto their backs; you won't be able to keep it from neighbours that you have a working generator or enough food to not lose a huge amount of weight if food becomes scarce.
If you understand a bit of science, though, you'll be able to survive for a while. Recognise edible wild plants, learn how to grow some edibles indoors, learn to hunt if you're reasonably close to the countryside, learn how to preserve food, learn to cook with fire or produce makeshift candles, learn how to distill water, learn to sew and mend stuff, learn how to make even primitive batteries. Those skills will get you far further.
Of course, all of that is pointless if a war turns nuclear, but if we've learned anything from the past (and humans rarely do) then any country even considering going down the route better research air currents, because the stuff rarely stays localised and there is no point ruling over Eurose if most of it is irradiated. New nuclear bombs are, after all, quite a few times stronger than what was dropped onto Hiroshima and Nagasaki.