1. always have weapon change at "never" because while you are legging it to the exit shootin your way through endless amounts of splitters, you don't want to have a shotgun equipped and suddenly walk over a pistol to suddenly change weapon!
2. in some levels some things are explosive. try shooting everything at first.
eg: say someone was behind a wall. you knew they were there, you just couldn't see them. there is a barrel near the wall. if the barrel is close enough, blow it up and it could kill the guy behind the wall.
3. you don't always have to fight. take the mansion level. you walk into a room, and the dear heads start shooting at you. they are incredibly hard to kill. remember, you don't HAVE to kill them. take a zombie. you can only kill it by shooting it in the head. shooting it anywhere else will stun it. if you are cornered, stun them all and leggit. they aren't smart enough to follow you.
4. if you stun a zombie when you were aiming for its head, it can still be killed whilst it is recovering/lying on the floor. you don't have to wait for it to get up again.
Submitted by Games Masstur