Some things in Survivalist are a bit non-intuitive. Take these tips with a grain of salt
Shoot at the legs to slow zombies down, shoot head for most damage/one-shots, avoid shooting body to preserve vests.
Sell a stack (200) of corn and buy back, repeat. Congrats you've reduced prices for everything else, and maybe only cost you 40 gold (depending on existing Approval and Respect).
The looters that you clear out for the Fat Neill's, you may find split up with 4 at the front entrance, 1 in a watchtower at the back and 1 in the middle, who seems out of reach. Explore all around it, they are all reachable and then you can open the gates.
Save on ammo by kicking zombies to death instead.
Go to Options Controls and read through the whole list of controls. You may find some useful features you haven't seen yet.
Zombies rarely respawn in areas you've already explored. Take advantage of this and run through these areas to save time (never mind fatigue).
Some nice tips and pointers: http://www.indiedb.com/games/survivalist/forum/thread/another-couple-of-questions