What's your best burger recipe? Trying to impress a guy.

This is lame, but I've been dating a guy who is obsessed with finding the best possible burger there is and I want to show off for him. Normally I just get some beef from the grocery store and season it with the normal McCormicks, salt, pepper, etc.. I've only ever gotten compliments on my burgers. But I really want to take this to the next level when he comes over to grill later this week. I need all the tips - I'm willing to go to a butcher, but what is the best fat ratio? Is there a best spot on the grill to cook perfectly? What is that secret ingredient(s) that will really take it to the next level? If it's a factor, I have a little Webber charcole grill.