Basically, the idea is quite simple, 1 block in Minecraft equals 1 meter in real life. I didn't mention any other systems besides metric because that's the one we're going to use. And it's the easiest one to use if you want to build in a 1:1 scale.
So, how do you actually build it in Minecraft?
Step 1: find a real-world house that you want to build.
It's better if you use Google Earth for this, because you will need a lot of references from all different angles of the building, and its Street View provides just that.
Step 2: make the measurements of the building and area in general.

Let's say for this lesson we decided to build a house shown in red, in Rochester, New York.
Now, the reason why we chose Google Earth for this is that there is a measuring tool, you can measure everything with it and it will show the size and height in meters.

So here it turned out to be around 8m. (Note that sometimes we ain't that lucky and it might've been 8.5 m or 8.3. In such a situation, we will have to assume that it's either 8 blocks or 9 blocks in Minecraft, depending on what the building looks like, because for building in a 1:1 scale the exterior of the building is the first priority, even if the actual size needs to be sacrificed for it).
Step 3: build the plan in Minecraft.

This is how it looks like if you actually build it in Minecraft, with all the earlier done measurements.
Step 4: Exterior.
The most important factor in this step is the materials. More on that later in my materials guide, however, the basic rule is to choose the material by color almost always, not by its texture. Because the idea here is to make it as realistic as possible, and when you look at a building from afar, you won't see the texture you will only notice the color of the walls, of the roof and windows.

For this you will only need real pictures as references, to understand the color and window position, as well as all the other surroundings just in case. (Note that sometimes we might not know what the building looks like from behind, in this case just assume it and build on your own, no one will check anyway :D).

The general rules:
- Each floor is a maximum of 3 meters. This is really close to most standards in real life.
- Each window is either 2 meters, or 1 meter in height, depending on the shape. Minecraft texture of glass will really add realism to these types of windows.
- The separation between two floors is only 1 meter, not more than that.
Sometimes though a building might have a foundation of 1m, so in this example building does have a foundation in real life, however, it is too short to even consider it in Minecraft.

So we've almost got to the final stage.
Step 5: Add details.
This is basically the most important stage, and maybe the most fun :D. Just add what you see in there, buttons, wall blocks, chimneys, chairs, everything you can add from what you see in the pictures. The finishing touches.


Does this look similar? :D


However, here, to achieve the same look, same shadows and colors, I removed clouds, and put sun path rotation to -25, which is summertime, instead of winter (-65), and I set the time to around 9000.