If you are using a thin "flank"-type meat, up to and including the famous "London Broil", cook quickly, over fairly high heat and then allow it to rest, covered in a good-sized bowl for about 15 minutes.
Even Skirt steak the "faja" from which "fajitas" are made is delcious, tender and delish! Did I mention that this also works with venison, caribou and moose? It does!
For "good" steaks, (t-bone, rib eye, etc.,) the secret seems to be "don't go too fast". The old "slap 'em on a rocket-hot grill or pan to sear the juices in", is largely disproven, and what you really do, is char the outer layers, resulting in a chewy, damaged layer that isn't all that yummy.
Medium-high heat is the ticket, and, when you see juices beginning to rise to the surface, turn it. Then, if it is thicker than an inch, watch for juices again, and turn. I know, I know. Old-school grillmeisters will gasp and tell you "never turn a steak more than once!!"
Rubbish. Use the heat to keep those juices INSIDE the meat until it is the way you like it. 125 (F) for rare-med. rare, 135 for med, 140 med-well, and after that... who cares? You might as well save your money and eat baloney.
Always let your meat rest (snicker), and tenderness and juiciness will be yours!