actually, if you do enough of the same thing , you quite often have a good starting point
eg.
bright day wedding, when I want limited DOF, I'm at 2.8 iso100, CPL turned on, shooting 1/800
dawn's just broken, I'm at the coast, I want good DOF with 0.3 seconds partial wave motion , I'm usually at F11, iso has to be between 200-800 depending on lighting conditions and filters.
Experience eliminates alot of the guesswork (not all) and gets you closer to where you need to be for given situations