You have to try it out and practice, practice, practice. The cheap hot-air rework stations don't have calibrated temperature controls, and air speed as well as the nozzle have an impact, too. Oh, and distance from nozzel to component, and how fast you waggle the nozzle around. And environment temperature, preheating, etc.
Start with medium air speed, or if you happen to have a rework station with reasonable air-flow adjustment, try 20 l/min air flow for a start.
Use a nozzle for the particular package. If you don't have an exact matching nozzle try the next larger one. If you don't have one, use the standard 5mm diameter nozzle for small components, and a large one or no nozzle (22 mm) for large components. Avoid nozzles smaller than e.g. 2 mm for a start, unless you really need to, because they badly affect air flow on cheap stations.
Start with 350 deg. If nothing happens or it takes ages, try 375 and then 400 deg.
Start with a distance of approx. 2 cm from nozzle to component. If you don't use a special, matching nozzle, e.g. if you just use the 5 mm nozzle, circle around the component. Don't keep blowing on the same spot for a longer time. Even if you use a special matching nozzle, move at least up and down a bit and rotate the nozzle if possible to avoid creating a hot spot (cheap rework stations have the "interesting property" that the heaters don't uniformly heat the air flow, because the heaters aren't mounted exactly centered. If you use a wide nozzle or no nozzle there can be a temperature difference in the output hot air.)