From Palmer's "How to Brew" http://www.howtobrew.com
When all is said and done though, single rest infusion mashing is the easiest method for producing an all-grain wort. The most common homebrewig mash schedule consists of a water-to-grain ratio of 1.5-2 quarts per pound, and holding the mash between 150-155F for 1 hour. Probably 90% of the beer styles in the world today are produced with this method.
To hit that temp there is some temp loss due to obsorbtion, and the walls of your mash tun coming up to temp.
Heres a little math I borrowed from BierMuncher I think:
"My normal calculation is to take my desired mash temp, add the grain weight, add 5 degrees."
So a 10 pound grist at a target of 152?
152+10+5=167 degree strike temp.
after tossing in the higher temp, and stirring fully to prevent doughballs, and your pot or cooler warms up - it ends up at the target temp. Slam on the lid.