Salt, pepper, olive oil, and a touch of garlic on any good cut of meat. If you're doing sirloins there is nothing wrong with a little marinade in a zip lock. A1 Chicago Steakhouse is good. If I'm doing something like flanksteak, I like to rub with salt, pepper, cilantro, fresh minced garlic, minced red onion, and minced jalapeño in a ziplock overnight. I'm trying to seal in flavors and aromatics. Next day I'll add some olive oil and work it in the bag before cooking.
No no matter how you season or what method you cook with, let your steak rest. I tear a big sheet of foil off and put it on the counter. When I pull my steak I put them on the foil, scoop a tbl spoon of butter on top of each steak, fold the edges up and loosely seal the whole deal. Set the table and the last thing I do is unwrap the steaks and plate.