Take the disgusting undead down with headshots whenever possible for an injection of bonus coins.

Interacting with objects (such as restoring barricades) will reward you with extra money.

You can always increase the difficulty level before starting a mission and thus earn more coins.

A few well-placed shots in red barrels and the explosive result will take out any nearby enemies. Just make sure you're not standing next to them yourself when you pull that trigger.

Any time you pass by an ammunition box, make sure you top up so you're ready for the fight lying just around the next corner. Simply point your targeting reticule at the box and hold it there to get a full clip over time.

When you see horde of zombies approaching look for the nearest barricade you can find, make sure it's fully repaired and keep your back to that. You may still be ambushed from behind, but you'll get an audible warning as the zombies try to chew through the barricade.

When you see that glowing red skull icon appearing on your reticule, move in the opposite direction immediately. This warning indicates that a nearby zombie is about to take a pretty meaty swipe at you.

The arrow at the top of the screen will do a pretty good job of leading you through each mission, but if you get stuck navigating your way through a particular section look out for the big shuffling dead things that want to eat your brains, and head that way.

Certain zombies explode when you kill them and you do not want to be standing next to them when it happens.