Depending on what you are cooking, how hot ( briquette or lump and if they are fully ashed over or not) the fuel, outside temp,...etc. Best way for me is to figure out the cooking grate temp using external thermometer. Usually. my lid thermo runs about 40 to 50 higher. I go about 1/2 to 3/4 open at the bowl vent and bit more on the lid vent. If I am off by 50f to more than 100f + or - from where I want it..... I will adjust the vents again but always more open on top for me. Once I get it close, i will fine tune it with just the lid vent.