I have two basic methods. One for sure on the grill and the other with a George Foreman indoor grill.
Outdoor - Traditional A-1 Steak sauce enough to marinate the steak(s) poured in a bowl then poured into a plastic baggie later, Worcestershire sauce enough gluggs to form a lake about 3/4 across the A-1 sauce surface, a squirt of mustard, a pinch of salt, and several hard shakes of pepper. Place in the baggie, massage, then let set at least 3 or so hours.
Indoor - A stout sprinkling of a store bought seasoning mix varying by mood, however a good bit of pepper, yet not a blizzard on one the top side only. Cleaning is easier with the wipe down process after grilling and only the bottom George Foreman grill plate needs being washed.