I find that I generally do NOT want org mode to execute source code
blocks as a side effect of exporting, which is the default behavior.
Rather, I prefer to explicitly execute the code either interactively
block by block (such as when I'm developing an analysis), or using
org-babel-execute-(buffer|subtree) commands. So, I typically set
`org-export-babel-evaluate` to nil on a buffer basis with the
following as 1st line in buffer:
# -*- org-export-babel-evaluate: nil; -*-