In a nuclear meltdown
The key is timing. You have to know when it's going to happen. Then you van evacuate in advance and start clearing out all the land around the event
Potassium iodine pills is one of the most common ways to rid radiation(radaway)
Lead can also be used to block the effects if it can be found
Unfortunately it is necessary to kill surrounding wildlife. To prevent mutations and radiation spreading
Unfortunately in most cases it is almost impossible to evacuate from these. The best thing to do is try and find a bunker(vault)
Like before the best and most common method of protection against radiation is your trusty iodine pills and lead coverings
After the event expect mutations. Some can be extremely violent and can cause damage to health
Eliminate these mutations with extreme prejudice.
And no matter what, Always keep hope. No matter how bad the situation.