A Kingdom for Keflings

The castle is the last blueprint and this must be done in Single Player campaign, build your way to the end, build the castle and connect it to it's three parts, remember to use castle walls! The parts you can use is Main Well, Arsenal, Residential tower and Chatelet.

Video: (Thanks to YourGruntLord)

Skip to 1:30.

As the other solutions say, this is the end progression goal of playing through the game normally and the game tells you the mechanics of what to do. You can always get the single-player achievements if you just play long enough and build all the buildings. It's just a question of how long it takes. What I'll try to do, therefore, is provide some tips on how to play the game efficiently so that you can build your city faster.

This is "all the things I wish I knew before I started building my town."

First, know that there are basically five types of buildings, some of which you care much more about than others. They are:

(1) The resource supply chain. You care the most about this and most of your interactions will be between this and (2) below. There are four resources in the game: wood, stone, wool, and magic crystals. Each resource has a refinement (planks, cut stone, etc.), and each refinement can be further refined. You need to harvest raw materials and, for most of the game, feed them through the next stage or two stages to refine them.

All the processing buildings produce processed resources in a specific square on their right. You can drop resources into a building from anywhere. Therefore, you should set up four left to right processing chains, with the first round of processing on the left and the second round on the right, with space between them so that you can walk between. The goal is to be able to pick up processed resources from stage one, turn around, and then drop them off in stage two. If you do this as your avatar and you have the buildings laid out properly, this is extremely fast and you often don't have to devote a Kefling to doing this. Be warned that all the processing buildings are small except for the second round of wool processing, which is a building that's vertically long, so leave room for it.

(2) Buildings that construct things. There are three core buildings that you use for the entire game: the basic workshop (which takes unprocessed resources), the contractor's office (which takes the first round of processed resources), and the factory (which takes the second round of processed resources). Put the basic workshop to the left of the input to your processing chain, the contractor's office above the open path between the two levels of processing, and the factory to the right of the second level. You will use wood and stone by far the most, and crystals and wool much less, so plan accordingly. (The factory will also need some single-processed crystals.)

There are also three other construction buildings that you'll use only at particular points in the game and then stop using them: the town workshop, the keep workshop, and the castle workshop. Where you put these doesn't therefore matter as much, but the town workshop is before the contractor's office, the keep workshop is between it and the factory, and the castle workshop you'll probably want at the same point in the chain as the factory.

There are also two other construction buildings: the garden shop and the sculptors. (There may be something other than the garden shop if you take a different path than I did.) You'll use these only once or twice in the game, so where you put them doesn't really matter.

(3) Game management areas. The town square and the building where the mayor/lord/king is (you add on to it at several times in the game). You will visit these periodically, but not intensively, so keep the close by but out of the way of your resource chain. Be warned that for the endgame you'll need to grow the Town Hall into a much bigger building and then connect four (total) other buildings to it with various types of walls. You want to build as few walls as possible if you're trying to be efficient, so leave room!

(4) Educational buildings. The primary school, secondary school, and guild hall you'll need to take Keflings to from time to time, but only once per Kefling. It's convenient to have these next to each other and away from everything else so they're not in the way.

(5) Everything else. It doesn't matter where you put the other buildings in the game, and once you've built them, you'll generally never go to them again. So don't put them next to where you're walking! Nothing is more annoying in the late game than constantly dodging around the roof painter's house because you put it right in the middle of what you're trying to work on. It's worth the effort to carry their parts off somewhere out of the way when you build them.

The rest of the game is about effectively using your Keflings. You could do almost all the game just with your Avatar, but it would be tedious and boring. The purpose of your Keflings is to do the things that are tedious and boring. Here, in order of priority, is what you should use them for:

(1) Staff buildings. This is the only thing that you absolutely have to have Keflings for and cannot do yourself, so obviously you have to use them. Most buildings need a Kefling to stay there to do their thing. You can build one of the non-critical buildings, get the blueprints to unlock, and then destroy it and get the Kefling back, but I never bothered; you have enough to leave them in the buildings and keep the building bonuses.

(2) Harvest resources. Your Keflings are almost as good at this as you are, and doing this yourself is unbelievably tedious and annoying. Don't ever bother. This is the main thing you should use your Keflings for.

You can train a Kefling to harvest a resource and then also carry it to where you want it. DON'T DO THIS. It's ridiculously inefficient. Harvesters should only harvest; they should stand there and build a pile of harvested resources. It's faster by far to have one Kefling harvest and another carry than it is for two Keflings to both harvest and carry, since they can carry more than one at once but won't if they harvest and carry.

(3) Carry resources from where they're harvested to the basic workshop or to your processing chain. You're much more efficient than your Keflings at this once there's a pile since you can carry more at once, but the resources are out at the edge of the map and it's usually way out of your way. If you have enough raw resources, have Keflings do this for you. I always have some Keflings carrying wood and rock, but sometimes don't bother for wool or crystals if I don't have an urgent need for them at that point of the game.

(4) Carry resources between steps in your processing chain and to the workshops. This is the first thing to take Keflings off of to do other more useful things. If you have your buildings laid out, you can do this fairly efficiently yourself. If you have the spare Keflings, by all means have a transporter to some of this, but if you run short, it's not that big of a deal. Keep them harvesting raw materials instead -- you'll need them!

One final tip: always pay close attention to the mayor/lord and always make his missions your top priority. He's the way that you get more Keflings, which is obviously a useful multiplier factor, and he gives you lots of useful stuff like items that let you walk faster and carry more, which make the game less tedious.

Enjoy! It's surprisingly addictive. :)

Castles are your last blue print. Also requires a castle workshop.
After you have built the castle the 4 items above it on the blueprint page in a tier can all be linked to the castle via castle walls buildable at a castle workshop. Simply make 2 walls and 2 of the parts and attach to the castle.

Keep building each building. You'll eventually get a chance to build a Castle. You'll have to attach two buildings to it to finish the castle. The game will tell you which buildings you can choose.
This achievement is pretty straightforward.

Just wanted to make is clear, as I made the mistake of making a TON of Keep Walls before realizing the castle walls existed. USE CASTLE WALLS, they are available in the castle workshop