He occasionally posts
rambly thoughts on design and mapping on the Youtubuals. I found this one made me pay more attention to the design than I did when I played the map itself.
In terms of knowing where to start, it's often useful to start with realism until you get more comfortable taking creative risks. Go look at some hallways and reference photography. What
would a laboratory have in its hallways? What purpose does the hallway serve? Where would the staff take a break? Can all this big heavy equipment get into a room without a loading door? Etc etc.
Once you're more comfortable with the tools, you can get much more creative and make choices without needing the references.