UFBG, Welshrarebit gives some great advice. I have an significantly older One Touch that does not have a temp gauge in the lid. When I "grill" I put my two charcoal baskets off to one side to form a circle and fill them with hot coals completely. All vents are fully open. I sear my steaks, burgers, chicken, whatever for the length of time desired, then move the meat over to the indirect side of the grill to finish. When grillin' I don't bother looking at temps at all. Time is what I use to figure out when it is done.
Now, when I smoke in
the Kettle temps are important. I have a Smokenator in my 22.5" to use as a heat fence so all the heat rises and circulates. I don't use the charcoal baskets in the Smokenator. In my now defunct 26+ year old 18.5" I just used a couple of fireplace bricks as a heat fence, putting the charcoal baskets curved side against one side of
the Kettle to form a crescent shape. I load the baskets or the Smokenator with cold charcoal and wood then only put about 10-14 hot coals on top of the cold charcoal. Bottom vents on the One Touch are fully open. On my old 18.5" that had three bottom vents I closed off the one opposite the fire and left the two directly under the fire fully open.
I turned the lid so the lid vent was on the opposite side of the fire to encourage circulation and controlled the grate temp purely with that top vent. I thread a Maverick chamber temp probe through the top vent and attach it to the grill directly underneath the top vent.
At lower smokes like 225F there can be a 30F difference between the lid temp and the grate temp, the grate temp being cooler. That difference goes up the hotter you are running your Kettle.
The trick is learning how to control the temp with that one top vent. I usually leave it fully open until the temperature climbs to within 15 degrees of my target grate temp then close it down to about 1/4 open and let it stabilize. If using a Maverick you'd be amazed at how easy it is to control that temp to + or - 5F making 1/16" changes by opening that top vent to increase temp or close it down 1/16" to cool down your temps.
Initially I chased temps quite a bit, but quickly figured out when to make those top vent adjustments to catch the temp just where I wanted it. I can keep temps steady for about 90 minutes now before I see any movement.