The Radioactive Fallout Problem
Initially the radioactivity is very intense, but it will decay by a factor of 10 every factor of 7 in time. An initial radiation level of 1,000,000 units /hr will decrease to 1 unit/hr in about 2 weeks.
If you absorb more than 400 units, your life to death survival ratio is about 50 %. The best thing to have is a radiation detector, so that you can measure the local radioactivity level, but of course most people do not own such devices. You will have to rely on your local civil defense teams and announcements received on your battery powered radio.
You will need water. Bottled water and canned goods are not effected by external nuclear radiation. If the fallout dust gets on your clothes, shoes, or skin, wash it off immediately. (Do not bring the dust into your shelter). Fallout, will not make you radioactive, unless you eat it. The external fallout emits gamma rays (like x-rays) that penetrate your body and destroy body cells, but they will not make you glow in the dark.