I use Montreal Steak seasoning on mine.
I fire up the grill and get the temp to about 500 degrees.
I start with a cast iron skillet with some butter and minced garlic. I melt the butter, add the garlic and when it starts to turn brown I add the seasoning and I drop the steak on the skillet for about 90 seconds, turn and repeat for another 90 seconds.
After that, I take the skillet and put it in the grill for about 6-7 minutes for an 1.5" thick steak, 3 or so minutes per side.
Perfection.