Beyond what was mentioned above; patience and practice. Trial and error; and Mix N match.
For myself I generally mix n match trial & error. Which basically means trying out blocks side by side to see which I think look nice beside each other. I mainly only work with the smaller buildings or medium sized ones. Potentially though I could expand it to being something large... Regardless, mainly work with a framework in mind then think function or possibly structural integrity, but not necessary. Using pictures of something else can help practice, as rl pictures sometimes help the inspiration, if not transcribe the building or what ever the picture is of using the blocks. That is where mix n match trial and error would come in handy.
Of course I just use what I have, and always aim to have as many different blocks to work with as I can. Usually starting with the easiest which is the many different wood types, even the one from the traveling merchant; although have not worked with that one much as of yet beyond making some of the furniture out of it.
Usually there is a primary block used and a secondary that is used. That is roughly how I do the foreground walls. The ones in the background I just come up with some basic patterns I use, some which are semi-random and uniform like I guess... Well thinking of my mine shafts & tunnel that I habitually decorate to look the part.
Sometimes mimicking a pattern can draw on inspiration or a way to go about some of the many things you probably seen. It really all boils down to personal taste and a good eye to tell the difference between each material and how they look. Granted some could memorize all the looks of the blocks and such, but me personally I could not really do that all at once. Hence my trial and error experiments; by placing material next to each other to see a difference or likeness for future design or pattern. always trying things out just to see how it would look with this or that.
I know that is a bit to read, and no expert, but I do build more than I progress in this game...><