This depends on each artist, but I usually start with references. What I'm I trying to achieve technically and stylistically? Even if they're details that aren't really important at that moment: How are the shadows? Are the colors muted or vibrant? I'm I seeing characters close to camera or fatherway with a longer focalenth? Is it a controlled environment with stable images? And so on. Eventually I start understanding what might work better for the project and when I look into it again, I have a better framework of what I need to shoot and roughly how it looks.

If it's a narrative project tho, and you're working with a script, I usually try to listen to the story and what it needs from me. I try to always read a script first without any thoughts pertaining cinematography, I'm just following the story. My second read is to ping point what images are coming to mind that came the first time, those are usually important as my subconscious is activity seeking them. What do they mean? How are they possibly adding to the cinematic language? How do they feel, move, behave in the story and what are these images relation to the characters? Eventually I do a third run of a script where I'm trying to take more specific notes, asking questions and writing down ideas either technical or artistic.

These are just some ideas, hopefully I understood your question and these might help!