Zombie Fighting Tactics - Selecting Terrain

Zombies only have one tactic. They mob their targets.  If they can see you, hear you, or smell you, they will advance on you.  All Zombies that sense you will shuffle directly towards your group in order to satisfy a primal hunger.

ZombieWalk photo by tangi bertin from Rennes, France (La HORDE progresse  Uploaded by paris 17) [CC BY 2.0 (http://creativecommons.org/licenses/by/2.0)], via Wikimedia Commons

If you are going to fight Zombies, it's best to fight on ground of your own choosing.  If you want to prevail, make the Zombies cross difficult terrain.  If you put a steep ravine between you and them, many may fall and break legs, ankles, or hips.  If you put a swift flowing river between you and zombies, many may be swept downstream when they attempt to cross.  Zombies will fall into pits, impale themselves, and damage themselves in an attempt to get to you and eat you.  You also want to channel zombies into approaching from directions where you can hit them, but they can't easily hit you.  As in all warfare, the high ground provides defenders with an advantage.  For example, clumsy Zombies might have trouble navigating the steep rocky slope of Little Round Top at the Gettysburg National Battlefield Park.

The Steep Rocky Terrain of Little Round Top at Gettysburg, Pennsylvania Little Round Top photo by Jan Kronsell, July 2002 {{GFDL-self}}

Since Zombies will damage themselves trying to get at a food source, it just makes great tactical sense to put damaging obstacles between you and the Zombies.