first pick up all avalible people that arnt infected and tell them to bring all weapons as they possibly can.
then find a safe location to set as a base then have a small party go to a locial grocery store to pick up food. then to a sporting goods to get all the guns and ammo there then try to survive off that for as long as u can.
Depends on where you are
personally, Im located in canada, alberta. I have mountains nearby so in the event of an outbreak Im headed straight there after gathering weapons and supplies. Set up camp there, fortify an area and bide my time
I will gather as many survivors and weapons and try to get out of the city as soon as possible, then i would head to the nearest military installation and fortify it as best i can. there we would have food and ammo to last for some time. once we had the place as secure as possible i would send out search teams to near by cities and houses to look for other survivors. eventually we would have to raid the cities for supplies anyway so we might as well pick up survivors too