Ammo is obviously vitally important in ZombiU as the easiest and safest way to take out roaming zombies. You should preserve your ammunition for when taking on larger groups of zombies.
A great way to take out zombies without using ammunition is to use the surroundings to your advantage. If you find a fence that zombies have to crawl under or objects they have to clamber over, stand on the other side with a baseball bat and smash some skulls!
Be aware also that you can lure the bomber zombies towards others and then blow up the gas tanks that they carry to take out additional enemies without wasting extra bullets.
Rather than using bullets on huge crowds of zombies, deploy blanket weaponry such as flares to draw in the enemy, then grenades, molotovs and mines.
Added by: MongooseGeneral Dec 17th 2012, ID#31