Leave the city

It is important that in the period of peril you be far away from major population centers. John Titor said you should be at least three days walk away from a city.

Why to move to an area of low population density.

Please remember when you build to make your shelter deep underground and far away from roads as anything new will attract undue interest, as always crime will follow new construction. A new road or structure will change the amount of crime in the area, by increasing it. For example, if you got a weed ridden abandoned field that nobody visits, with few people around and nothing valuable to take from it, chances are that their will be little crime in the area. Also, if the roads are poor quality and not maintained, few thieves will venture. They want a quick get away and lots of stuff to move.

Remember that after the crash there will be few if any authorities to protect you, so being in a remote rural area will increase your chances of being able to survive.