I'm not sure how one could ever classify "the best" steak, with so many cuts and their various strengths and weaknesses, but if I had to pick just one way to steak it, this would be the way:
1) Start with a well-marbled, dry-aged, USDA prime sirloin or strip
2) Drizzle a
light coating of oil
3) Lightly salt (iodized is NOT ok) to seal juices, then rub with cracked peppercorns
4) Crank the heat and sear on both sides with a skillet/plate,
never flip more than once and
only with tongs, never a fork!
5) Don't eyeball or ballpark it and never cut in to determine how it's cooked - Use a meat thermometer. When it hits 140 degrees, take it off the skillet/plate and let it rest for 5 minutes so the juices sink back to the outsides of the meat from the center.
6) Drizzle ever so slightly with balsamic glaze if desired.
The end product should be browned on the surface (but not
burnt) and a perfect medium-rare inside - And with the dry-aged beef, the outside fat should be almost crispy like bacon. If you absolutely insist your steak be cooked beyond medium-rare, take the skillet off the top and finish it for a couple more minutes in the oven so the surface doesn't burn.
If you desire onions/mushrooms/peppers/garlic/shallots/etc.- cook and season them to taste separately and lay over the top only once the steak is finished. A balsamic or bordeaux reduction is fine, but make it with your vegetables, not with your steak, so you don't taint the flavor of the beef while it cooks. The meat should always be able to stand alone - if it doesn't, you didn't cook a good steak, there is no covering that up.
A1 only exists to cover up the taste of shitty and/or overcooked beef. If the cow knew you were pouring that junk on otherwise, it would've kicked your sorry ass for abusing it's marbled goodness.
EDIT: Nothing wrong with grilling a steak over flame, but sear it and seal it first, dammit.