Okay, I am a steak lover, and my steaks rival the best steakhouses. Yes, I said that out loud.
First, the cut of beef is extremely important. The tenderloin, AKA Filet Mignon, is the most tender. But, it is also one of the less flavorful cuts, so you will need a lot of seasoning, and probably a sauce.
Sirloin is cheap, and has great beef flavor, but it can be tough.
My favorite cut is ribeye, AKA Scotch Filet. It has good flavor, and is tender.
As for cooking, the best tenderness and taste will come from a medium rare cook (rare will be more tender, but can also be "mushy").
As others have mentioned, cooking steak "hot and fast" is the best way. On an outdoor grill, get a good bed of hot coals going. Indoors, a very hot cast iron pan is a good way to go. I use sous vide, followed by a quick sear, but if you don't have the equipment for that, it won't help you.
Always start with a steak that is completely thawed, and preferably at room temperature. Don't worry, it is perfectly safe to do that. If your steak is ice cold, it will burn on the outside before it is properly cooked inside.
As for marinading steak. If you are using a budget cut, like sirloin, a marinade will definitely help tenderize the meat. For tenderloin or ribeye, it just isn't needed.
This is just the basics. There are a lot of good videos on YouTube about cooking steak, and most of the ones I have watched have been pretty good.
it is really not difficult, once you know the basics. Once you get the hang of it, it is actually very easy to cook a great steak.
CD