All of these comments are spot on. Another trick to getting great grill marks (if your grill cant reach the 450-500 degree mark) is to incorporate a little sugar into your meat seasoning. The sugar will carmelize once it hits the grates and will create some pretty intense grill marks and if done correct a nice flavor profile as well. Just a thought.
"Life is a Shipwreck but we must not forget to sing in the lifeboats"