In a short answer, if the pan smokes, it's too hot... What'd I'd play with is getting a batch of throw-away (something), for instance biscuits or something with the intent to test your stovetop. Heat the pan to different temps and see what happens to your throw-away food when you put it on the pan.
In short though, smoking is bad. And if it's teflon, it's doubly bad as teflon is only rated for stovetop temps. If a teflon pan gets too hot, the teflon becomes dangerous.
Also, in the context of your answer, "Too hot" is relative to the specific food you're trying to cook... Usually you can drop a few drops of water in an empty pan and watch how fast the drops "skid" away. You'll want it to skid away at different speeds based on what you're cooking.
Editing to put some reference to the teflon comment
These things also make it good to coat a frying pan with. It’s very inert, so it won’t do anything to the food or, more importantly, our insides. It is durable at high temperatures where other plastics would melt or burn. And of course it is extremely slippery.
If you swallow bits of Teflon they won’t hurt you. It’s just plastic. If you burn Teflon, though, things are different. When Teflon is heated too strongly the resulting fumes, for reasons not yet fully understood, are very bad for you. Fortunately it’s hard to get Teflon too hot, but it could possibly happen if a coated pan is left dry on a hot element or in a very hot oven. So don’t do that.
Nothing sticks to Teflon, except the unfounded rumour of its toxicity. But, like the burnt cheese in a frying pan commercial, even that just wipes right off.