All you need to do is season both sides of the steak with salt (preferably kosher). Avoid marinades (that's for chicken and stuff you'll put in an oven, not the grill), fresh herbs (includes ground black pepper; they burn too easily) and dried herbs (if I want a salad, I would be eating that instead).
Make your grill as hot as you can get it (charcoal would be great, but a gas grill will work as well) and grill it to medium, following Andrew Barnes' instructions.
By the way, I can't emphasize this enough, so I'll put it in capital letters below.
MAKE SURE THE STEAK IS ALLOWED TO REST OFF THE HEAT FOR AT LEAST 5 MINUTES BEFORE SERVING AND CUTTING INTO IT.
Why? The juices in the steak are flowing like blood is in your veins. Allowing it to rest will let the steak settle those juices down, so they won't spill out of the meat and take most of the flavor with it.
Ignore this step and you will have a very dry, bland tasting steak (possibly tough if you INSIST on grilling it any higher than medium) sitting on top of what Alton Brown would call "a liquid pool of love".
If the steak is done right and allowed to rest, that juice will be your steak sauce. I guess you can make some au jus out of any drippings if you must (the how-tos will wait for another episode), but if you buy sauce off the shelf, it better be because someone you're going to visit makes terrible steaks and you don't want to insult him/her by saying they taste like cardboard.
Like your steak medium well or well done? I got a suggestion (don't mean to be rude here, so sorry if it sounds like it), get over it. If you like it because food poisoning isn't an issue, I've got something to share with you. If the steaks were handled correctly at the store (or at home if you cut your own), food poisoning chances are extremely low. And even if there was any bacteria on the surface of the steak, we just doused it with salt and put it on a 700 degree grill for 10 minutes. There is absolutely no chance anything that would result in you counting bathroom tiles will have survived that. If you like it because of the taste, you don't know what true steak is.