If you are in the city then take the hight ground... get together with a few friends and find an empty building.... secure the first and secondo floor and don't forget any entrance to the basement.

At the first time of troulbe start by taking as much water as possibe and also empty containers to collect rain water...

Also start taking all your food and equipment and be sure that someone (with a weapond) stays there at all time till you move in for good.

Be sure that building is taller than any other in that area and post guards at the 12 and 6 on the roof... same as downstairs but at some distance from the building and with radios.

Set booby-traps in all rooms in the first and second floor and make sure that there is only one way to get into the building and only one way to go upstairs.