I use to put about 4-5 ounces of water in a pyrex cup, then nuke it to boil. Cover it with syran wrap and let it set to cool off. I usually did this at the start of brewing so that it's cool to the touch by the time I need it. Dump all the yeast in the pyrex cup and let sit for about 15 minutes then pitch. Notice I said "use" to. Now, after reading about this method from others here, I simply dump the yeast on top of the wort once it reaches room temperature. I've never had a problem doing it this way yet and that's been about a dozen or so batches.