Invention Heuristics are techniques writers use to get started on a document rather than procrastinating. Writing faculty sometimes refer to Invention Heuristics as Prewriting Strategies.
Whereas Drafting refers to a writer’s effort to actually write a document, maybe a first draft or even a sentence or two that has the kernel of something larger, Invention Heuristics are a bit more playful and experimental.
Invention Heuristics are sort of like an athlete’s warm up exercises. For instance, a writer could write a reflective note about the rhetorical situation or maybe as work plan for drafting and collaborating. While reading, the writer could draft a book mark about the status of scholarly conversation about the topic. The writer could conduct even a bit of metacognitive work about whether the project is really worth doing.