Princess, Buckalew, Rnmom, and some of the others are right on!!!!!!!
1. Buy a GOOD cut of steak... Cheaper beef will be tough.
2. Let it sit out of the fridge for a while, so that it is closer to room temperature. It is never as good to cook ice cold beef or chicken.
3. That cast-iron grill pan looks wonderful!!! Your regular cast-iron skillet would still be great.
4. Preheat your skillet till it is HOT.... HOT enough to immediately begin to 'sear' your steak, like a hot grill would. This is important. If you are trying to cook steak on a George Forman grill, that is your problem... NOT hot enough to sear in the juices... and has to cook for far to long to reach your desired done-ness.
5. Sear/grill the steak on that hot preheated skillet, with just a dab of oil, for just enough time till it looks as done/browned as you like. As one other poster mentioned... You can have the broiler on your oven preheated very hot... Use the skillet for just like a couple of minutes on each side... and then place right under that broiler.
6. Do NOT cut your steak right away... Now, you don't want steak to sit... because that isn't good either... But just make sure it rests/cures for a good full 2-3 minutes before you take a knife to it. This is what lets the steak re-absorb and hold some of those juices that you have seared in!
This is a pet peeve of mine with my husband... he is pretty good at grilling while I prepare the sides in the kitchen... but, he feels like he doesn't know when it is 'done' unless he takes a knife to it right away as he is taking the meat off the grill. Believe me, this DOES make a difference.
It is up to you if you want to add a lot of seasoning or marinade...
But, for me, I like a good, delicious, classic steak. (please don't defile a great cut of meat with a heavy marinade!!!!)
I do a good coating of salt, a little garlic powder (not granulated garlic or garlic salt), and maybe some paparika.
Ohhh, and also don't defile a good cut of beef by cooking until it is mass of grey whit-leather.
Some 'pink' is always good!
Hope this helps!