If a scenario like that happend it would most likely play out as in the remake of dawn of the dead.
Confusion and chaos would rein making any co-ordinated effort of the living to fight them almost impossible.
So you would just have to get any supplies and weapons, and maybe some survivors (if their your friends, or someone you trust) and stay away from
urban or built up areas.
Maybe barricade yourself in an isolated defendable building, and then wait the whole thing out.
Yes that's right I have plan in case of ZOMBIE ATTACK! after seeing the remake of dawn of the dead im always looking over my shoulders when im on my
own, and i always stay away from corners and driveways that one could suddenly jump out of, it's stupid i know!