GotGarlic
Chef Extraordinaire
Yeah, but what did people do before thermometers were redily available?
There used to be a lot of food-borne illness with its associated intestinal discomforts. Or, in some cases, death.
Yeah, but what did people do before thermometers were redily available?
Chief, the OP wanted 'general rules'. I contend there are no reliable 'general rules' because of the variables. Yes, a person can learn to cook it properly without a thermometer by learning the variables for himself. I contend that for the majority, this is not going to work.
I don't often grill chicken breasts, but when I do I drink Dos Equis.
Two beers and they're done
Seriously, you need to find your own general rules, or rule of thumb.
Bucky uses the bend or crack test, but he probably derived at this by testing with other methods (cutting into it, taking temp) and realized that the breast also cracked when it was done and barely bent when not. You need to start with a tried and proven method and then learn to recognize another trait the breast exhibits. For me it's smell. If it smells like cooked chicken, it's done to my liking.
But I still double-check it with a thermometer or by cutting into it.