I'd like to know when to take my steaks off the grill and please everybody.
I agree with the temperatures given for doneness by @BarrettJ, but especially when grilling flat cuts of meat like steak, pork chops, chicken breasts, etc., it's difficult to use even an accurate instant read thermometer to determine doneness. In my case, I grill on charcoal most often, and it's practically impossible to avoid hotspots. If I always relied on a thermometer reading, I'd have to test each steak or chop to know when I was done.
So, I'd recommend using the thermometer a few times, but pay close attention to how the steak feels when pinched or poked with a finger. Here is an example of an article that describes this with rules of thumb for how to tell roughly how done a piece of meat is. But rather than comparing how your steak feels with the firmness of the palm of your hand (as per the article), I'd recommend taking the thermo reading, feeling the steak, looking at how well done the meat is when it's cut open and adjusting accordingly on your next grill session. Soon it will be second nature, you can save the instant read for roasts, and your friends will deem you "The Grill Whisperer".