Don’t forget to actually collect the kill points zombies drop when they die.
Get those multi kill bonuses
Always upgrade weapons because upgraded weapons give you better damage.
Basic gun goes all the way to level 25, so don’t be shy to take it to at least level 10 (and replay the stages with it upgraded for a real blast!)
Always try to hit as many headshots as possible they give you more points and fill the frenzy meter faster.
Frenzy gives you a lot more points to fill it faster, get headshots and kill ranged zombies in order to fill that bar as fast as possible.
The best strategy to approach Attack stages is to move forward and backwards in a straight line – as soon as you reach the end point, tap the bottom of the screen (180 degrees turn) and start shooting at the zombies that have most likely started towards you.
When approaching Defend stages things are a bit more complicated since there are 3 points that you want to protect and they might not be available in a straight line.
If the zombies break in, you don’t lose the stage or something: they just all come at you and you can shoot them down from point blank range.