I hope this topic will help make you a better architect!
Now lets get started
CONSISTENCY
Make sure your buildings keep the same design throughout-you don't want to switch themes in the middle of a build
REALISM
Keep your buildings realistic-don't make random ledges with no supports or realistic way of keeping it standing
SYMMETRY
Not all buildings use symmetry, and it's not always a good thing to.-If symmetry is used too much, it could look too plain, but if there is not enough symmetry in the building, then it could look too unbalanced. This goes with consistency and using the same block type.
TEXTURE
Texture is important because it shows the designers taste and how they handle a situation-do not use two block types that don't mix
ADDITIONS
The little things count-use bushes or flowers and lights(lamps, glowstone, etc) to spice up the atmosphere around your project
INTERIOR
To spice up your project even more, add furniture and rooms that would be in a normal house-create bedrooms, kitchens, and anything else to help add depth to the build
I hope this helped you make better looking architecture. I'll add pictures for examples later. Feel free to give me more advice for making buildings, i love it!