Now that I have a grill, time to use it.  I found this story on msn.com on tips for grilling

You may be thinking that you have heard all the suggestions and have your own way.  Maybe so, maybe not?  I didn't know you were supposed to make a dimple on the top of your burger?  Basically, a thumb print.  It keeps your burger flatter, not cooking up shaped like a dome.

Mark Stout