Your best bet is to find a location that is far away from a military base (especially air force), missile silos, major population centers, nuclear reactors, and is not downwind of an area likely to be heavily bombed (fallout and all - though this will reduce significantly over time).
There used to be a lot more fallout predictive maps online, but I suspect some of them are out of date due to decommissioning of bases and silos. Some of the maps differ wildly as well. One area I see consistently safe from fallout and targets is the Rio Grande Valley area, though you'll want to stay away from El Paso due to potential targets of White Sands Missile Range in NM and Fort Bliss. Laughlin might also be a target, but yeah.
Something else to consider is heavily forested areas near target zones - those could be uncontrolled wildfires.
Essentially, if you live in the northern hemisphere, your best bet it to be near ground zero, because survival is going to suck in any significant exchange. Also, if you can't grow your own crops, slaughter and cook meat, and cannot defend yourself ... you can survive the initial days, but your chance for survival will be low.