I can try and explain what i do when im designing a building…
I almost exclusively use single blocks Since they are forgiving
You should always save before you consider placing any kind of wall.
The times you should consider walls is only when you want to place windows and doors. I have 2 ways of doing this either i try to push every wall placement to the end of the building and then make cut outs in the building then add walls, windows and doors. (the safe way) the less safe way is when im almost 100% positive something has its final look. I might save and add the details and continue rest of the building.
If im doing somthing new i will start out to find at least 3 matching/fitting colors.
Many times i will then draw out a simple floor plan, mainly for the world around the house. that way i get a rough idea of both possible shapes and size in comparison of the world. (eg:other houses terrain trees ect)
About this time i will mostly roughly decide on the height of a building. with that knowledge i can mostly start drawing outlines of a house…if i cant draw the entire shape of the building just a rough size and outline for one wall is a good start.
Since that gives me a blank wall…and then i start trowing shapes and colors at the wall to i find something i like.
And then try to build on that…
Heres an example on the building im doing right now.
first pic is an almost done facade, it was pretty much a flat wall with 2 small pillars. That looked okey, but once i started adding the terraces. it was clear i needed 2 more(for supports for the terrace) But those 4 lines gives me natural smaller building zones. I can then fil these with windows, door, pillars, supports, terraces and stuff like that
.
And the smaller working space tempts to give me faster progress since i have less options.
combine that with the shapes and colors of the building i mostly end up with something fairly nice and unique.
Second pic is just to show it has a blank wall more
3rd one is the wall im currently trowing stuff at…i noted out early on in the building that there was room for a tower or weird door or something in that spot…once i finished the first facade of the building i did the tower figured it might influence the facade look.
Roughly how i do it anyways…keep in mind im the architect not the engineer!
I dont really care if my engineering heartlings goes insane just from planning the scaffolding
If anything if they can build it ! its below my standards 
for reference heres the next step:
Since i kinda liked that 
Bit rushed but still decent.
and here are the final pass.
last wall wont matter in this case since another building will go here but if i had to do it i would just copy the other side.