Figuring out what to focus on is a continual process of reflection and elimination.
You can't get a sense of what works without trying a lot of things.
When getting started, rather than attempting to guess exactly what to do — a more robust way to approach things is to run low-stakes experiments in exchange for experience.
“People are trying to be smart—all I am trying to do is not to be idiotic, but it’s harder than most people think.” – Charlie Munger
It's just as useful to figure out what not to do.
As your experience increases, so will your ability to spot opportunity, and combine the breadth of your experience into something entirely unique.
This is not a process that ever reaches a conclusion, but a model to overlay on the experiments we run — to figure out which ones to run again, and which ones to drop.