Don't rush into placing down your flag, explore a bit, find a nice spot, beachside view optional, and start building. Avoid dying before your flag is placed though, as if you do you will respawn in the standard start position so unless you started building where you spawned (weirdo) you might end up losing your progress if you can't find you colony to be again.
Your colonists don't care what floor is under their beds or if they have a roof over their heads so in theory you could just make your colony in an open field. I wouldn't advise this, but I do this a large open space is ideal.
Note that you can use the wheat farmer tool to designate where your farms will go even if you haven't placed your flag yet.
Once you find a place you like and start setting up shop, but before placing your banner (see defence 101 for when you should be doing that) you should look for seeds in your stockpile and place a few down, grow some crops. It helps to have a larger buffer than you begin with for when you start recruiting.
Every colonist you recruit instantly uses 50 food, one unprocessed wheat plant is equal to about 0.5 food. If you want to start off by recruiting four colonists (which is what I usually do), you will want 200 food plus a food buffer which will last for two days (the amount of time it takes for crops to grow).
Somewhere in the region of 350 food is a good starting point.
When you do begin recruiting the first four colonists I usually recruit are a baker, two wheat farmers and a guard. You don't really need a baker unless you did what I suggested (a bit of farming by yourself before founding the colony).
Maths: note I don't have exact numbers but this is from my experience, 1 full farm is 100 wheat plants that grow over two days. This is about 50 food. If each colonist uses 25 food per day ( I dont actually know off the top of my head) then 1 wheat farmer can just support himself and one more colonist. However, in combination with a baker, one farmer and one baker can support approximately 4.5 colonists. Vastly more efficient, It's also worth noting that each baker can keep up with about five or six wheat field's worth of production (that's 500-600 plants).
If you really like maths you can turn that into an equation, as for the rest of us it's a good rough point of referance.
Sorry for the slightly weird section setup but this is where I will talk about where you put your banner, hopefully you haven't placed it yet (although I think you can move it if you do but don't quote me I've never tried).
In the game there is something called seige mode, and basically, you want to void this mode which is activated by walling off yor banner from the rest of the world. Once this happens more zombies will spawn and a lot more food will be used.
On the other hand how the hell do you protect your banner if you can't wall it off? Well, walling off applies to a plane measured outwards from your banner and down/up about eight blocks or so. So if you have a large enough gap (vertically) between your banner and wall then you will be fine.
Let me tell you the secret though, walls two blocks high are impossible for you, colonists or zombies to get over, but, so are any ditches two blocks or more deep. Zombies and colonists view these as impassable and will walk around them. However, ditches don't contribute to the "walling off" quota for seige mode since they are a lack of something being in the way.
In simple terms, build a two block deep ditch around your colony and you will be safe.
In more advanced terms, you will want to be able to get out to other resources or to expand, so, build bridges which are choke points for zombies to die in, then ensure you have enough guards at these points so zombies don't get across.
Bear in mind, guards stationed higher have a longer range (up to a point). So if you have a guard stationed on a tower five blocks high vs one on the ground, the one on the tower will always shoot first at the zombies.
But, you want a ditch so zombies can't get in, no walls, but you want the guards stationed higher so they are more effective? How to do all this at once?
Well, Thin guard towers, without attaching them to a wall (free floating if you will) still work and won't trigger seige mode. All you need are some stairs so the guards can get up to their post. Preferably stairs that are further away from the zombies than the guard himself. Simple so they zombies don't have it easy if they try get up to him to sock him one.
Written by SexyBadger.