Suggested minimum skills:
Medic 1, Firearms 1, Hauler 1
Suggested 7 items:
Armor of some kind, preferably army. 3 Shotguns. 1 Shotgun shell x10. Medkit. Z-Tracker.
Suggested tactics:
0. Move resources out of enclosed rooms and into the often traveled main hallway, even if it's one at a time. Barricade the doors of cleared rooms afterwards with the wood from already smashed shelves, because if there is no door, moving a shelf there is easier (and cheaper) then building a new barricade.
1. Use 'r'un! Enable run, move away from the zombie until 1 tile seperates you, then fire your gun and disable run, then walk away normally to recover some stamina. Unless the zombie moves faster then you do, in which case, keep running. If you get pushed out of the facility don't worry, that's better then being dead.
2. Use appropriate guns for your targets. Don't dump shotguns into enemies that can be killed with pistols, or you'll regret it when the bigger zombies show up and get plinked at with a pea shooter.
3. Go it alone. While seemingly suicidal, being blocked by a team mate will only get you killed. They will also add another zombie to the population if they die. Keep them gaurding the stairs if you must.
Suggested strategy:
Always attempt to enter with at least medical, firearms, and hauling skill. Preferably also strength, agility, toughness, high stamina, and martial arts. Use only your best armor and weapons. Before entering, dump a pile of medkits and 5-stack bandages on top of the stairs, and leave a clear exit to the street. If you leave the underground wounded, you'll at least have a chance for fast healing. Use the perfume on the street, drop it there, then move in for the stairs to reduce the chances of getting followed in from behind.
Always enter on full status/equipment, never while sleepy or under supplied. If you ever become sleepy, leave the area /break off your fight immediately and retreat to the stairs and leave the facility, and sleep on the stairs (and medical pile) until you have FULLY rested. If you become hungry, leave before you become sleepy. If your equipment is damaged (armor, melee, no flashlights/z-scanners, no spare ammo) leave and recover your inventory setup. Always explore the facility in an outward circle, so there are as few black areas between you and the exit as possible.
Always try to have a z-tracker, and always activate it when approaching a doorway for at least a couple turns. If zombies are blocking your way, always try to retreat into KNOWN areas while your z-tracker is active. If zombies are blocking your path to the exit, activate and keep active your z-tracker while you find another way around through a known area. If you do this and find they are still blocking the exit, lure them away and retrace your steps. If you have no alternate routes through known areas, disable your z-tracker and fight your way through, unless you can not fight your way through, in which case enable your z-tracker and find a way through unknown areas and activate your flashlight for easier searching.
If you're playing a 2x2 city size, all i can say is "Good luck!" because you'll only get the medication you need to complete the underground facility from army chopper drops... And make sure it WAS an army chopper and not black-ops. Always read and comprehend the message; "Supplies" good. "Something" bad.