My Building Methodology
Sometimes I have a vision of what I want to build before I ever start and it's just a matter of finding an adequate plot. Sometimes I look at the plot and bedrock and just try to visualize what it could be. Kind of like looking at clouds and thinking of what the shapes remind me of.
I only buy a plot if it is the maximum size (1500 for small, 3000 for medium, 4500 for large). Then I build whatever it was I was hoping to build without worrying about traps or guards. Most plots aren't going to be nice, empty, flat plots. I just work around what I'm given. Sometimes I can make the bedrock beneficial, sometimes I just try to hide it.
Once I'm generally happy with how the build turns out then I'll go back and add traps and guards. As a general rule of thumb, I'll try to leave 40-50% of the capacity open for traps and guards. Then it's just about efficiency. I like guards, plasma sentinels, and lasers because give the feeling of filling up a lot of space. Then it's just a matter of fine tuning as I prestige up.