A: You need manpower. Once you've scouted the best location, go hunt down a few hundred others to help you built and with it. You need not take whiny crybabies who keep on b*tching about how you couldn't lead a couple of bounty hunters to a house, let alone an army. If you MUST be merciful, remember to keep a close eye on these fools and don't hesitate to jail, imprison or, in extreme cases, dump these from your base. Keep in mind it is YOUR base, you found it, you built it, you bloody own it! Remember; one fool with no idea how to run a community and is all for killing zombies until there aren't any left could be the death of everyone you've learned to work together with. Recklessness will be the death of you.
B: Keeping the zombies as far away as possible: This is open to creativity, but effective ways are to lay down lines of defensive thingys.
These lines should consist of pits, barricades, walls, land mines, barbed wires fences and automated or remotely controlled guns.
This is one good method to set up the lines in in a circle or ragged circle around your position:
The base in the center.
Around the base, walls topped with defensive guns and/or snipers. Towers ALWAYS a good thing. The only ways in through these solid walls would be heavy blast doors numbering about three or four. Any more might be inconvenient to defend.
A moat of some kind, filled with something nasty. Maybe acid, magma, scorching hot water, or oil which can be set alight to kill trapped zombies.
An area of flat ground, connected with the grounds behind the moat via retractable draw bridges, which should also be housed within small structures themselves so that intelligent zombies couldn't make a clear way across the moat for other zombies if they managed to get across.
After this, barricades. If the undead are stupid enough to impale themselves on sharpened or spiked barricades, then make the mentioned alterations to the barricades. If the undead are to cute for such things, don't waste your time.
Next, make a deep pit that could not be crossed via jumping. Depending on how evil you are, fill it with stakes. You may want to put in some sort of way of crossing this from inside or/and outside, like another set of retractable draw bridges. These would need to be controlled bye even heavier towers, with heavy doors, and helipads on top so that those manning them could be pulled back if the zombies where starting to break in.
the outermost layer should consist of land mines. Lots and lots of land mines. The more explosive the better!
While not strictly necessary, you could also add signs with things on them like "All ye' braindeads, welcome home to hades" or "BEWARE! Zombie hotel in that there city ahead. Zombies check in, they don't check out!" Or maybe just something informing humans of the defenses in place. If you feel bored you could string up some dead zombies with various horrible injuries too.