Houseboat Eats: How to preheat your pan
http://www.houseboateats.com/2009/12/on-properly-heating-your-pan.html

6/15/10

I like the method for determining when the pan is the right temperature.  I don't like the attempted explanations; water and protein change much more than steel between 70 and 300 degrees.

There is actually a small ideal window of heat that you should be aiming for in order to prevent sticking, optimize browning of your meat, and develop a nice fond on the pan.