The viet cong used a variety of methods of protection against a superier in number heavily armed enemy,
see here for an example
http://www.angelfire.com/hero2/vietcong/
It would be advisable for us to do the same, modern armies do so with tank traps or strategicaly placed obsticles funneling troops, armour etc into specific killing zones. This makes it easier for small numbers or individuals to deal with a larger oposing force.
Guerrilla tactics being the best defence in a post apocalyptic world unless you have a band of armed, millitary trained individuals who can take on large groups.
The french resistance used the tactics to great effect during ww2 attacking lone guards, or single vehicles thereby minimising causualties and taking their weapons thereby enabling them to do bigger and better operations next time.
"Some say the end is near, some say we will see Armageddon soon...
I certainly hope we will, I sure could use a vacation from this silly shit."