Most of the zombies you meet will be slow and stupid. They're pretty easily taken care of unless you get swarmed or put yourself in a stupid situation and got caught. Happens sometimes, you won't win them all. Just keep a cool head and your back to something solid and you might make it.
But the little ones? The kids who are fast and nasty? They're a whole different breed. They're almost too fast for head shots, and you can barely outrun them in the short sprint. They can climb ladders and stairs, and we're pretty sure they can figure out doorknobs. If a swarm of kids ever got rolling on the outside, it would be tough to put them down. Best thing you can do (outside of some high ground they cant climb to)is get on one knee, shoot til you're dry, then take them on hand to hand. The upside is they're weak, so you can forget about being overpowered. Duncan swears his sword is the best thing, but I'll have to see that one in action.
Until the last one is killed, stay alert, stay alive. If it feels wrong, it is.