Repair wall and find survivors...find weapons next
Always repair first on the first day until it's around 80 to 90 percent done. Search for survivors next as they will provide a much better defense to the wall than you can alone. The final survivor you find that fills up your vacancy will have a Hunting Rifle that will provide excellent defense. Once that's all done or while you're doing it find weapons. Keep your primary weapon a weapon that you'll use to pick off the zombies as they walk toward the wall and your secondary to be a relatively powerful weapon to quickly finish off any that do manage to get to the wall to start pounding away at it. Example: M431 as primary while Shotgun is secondary. If you find the last weapon which I won't mention you'll be all set for the rest of the game. A great game all the way through.