Hot as you can get cast iron pan or grill. If indoors - make sure you have a hood & exhaust fan to the outside.
When the pan is really, really, really hot (a drop of water will form a ball, dance & go POOF faster than you can read this), plop a well seasoned rib-eye (beforehand pat the steak dry with paper towels & liberally apply kosher or coarse sea salt with some ground pepper - let rest for about 3 minutes - the salt starts to draw moisture out of the steak - before cooking).
Cook for about 3 min or until the side is nicely seared.
Now for the hard part - medium rare.
Take your left hand (if you are right handed otherwise reverse) & place the thumb next to the index finger. Feel the pad just below the thumb & then poke the steak with the same finger - that is RARE! Medium rare is the feeling the pad below the index finger feels like.
Pull the steak at this point, put it on a plate (warmed or not, really doesn't matter & let it rest 5 minutes. Then serve. Personally, I'd pull it at the rare stage if the steak is under an inch thick since the latent heat will tend to cook the steak a bit more than a 1" thick steak.
Even with the rest after the grill, I find it difficult-impossible to get the internal temperature up to medium rare.
I use a cast iron grill pan as hot as she'll go. Steak goes on, turning the steak 90 degrees after a minute to get charring instead of burning and those lovely crisscross charring marks. Turn the steak over after 2 minutes and do the 90 degree thing all over again. Total time on the grill pan is 4 minutes. Pop it on a preheated broiler pan into a 325 oven for 5-15 minutes depending on the desired doneness and the size of the steak. If you put the grill pan in the oven, you're likely to end up with well done.
My advice, guillens89, is practice, practice, practice. The more consistent your steaks are (same butcher, same cut) the more natural it'll become to you.
If you have a digital thermometer, a sheet pan & wire rack and a fry pan.....a fool proof method is the Reverse Sear Process. You can look up the process on the internet, or here.....or you can look at the thread below which will guide you and has pictures so you can see the results and what to expect.. Regardless of cut of steak, the process is the same.
I can give you specific details, as I do not know the temperature you are shooting for and the thickness of the steak. If you do not have the fry pan....you can finish on the grill.
Season with salt and pepper and bring steak to room temp - about 30 mins. Grill on highest heat setting for 3 mins on side one and 2 mins on side two. Rest for 5 mins. Medium rare if you're starting with a 1.25" thick steak.
If it's thinner, might need to adjust down to 2 mins side one and 2 mins side two. You're really just looking to make a nice sear on both sides with most of the cooking coming during the rest period from residual heat.
Cover the steak loosely with foil while it rests.