Cooking steak over wood coals is romantic. It’s authentic. It’s elemental. It’s simple. It’s also very easy to screw up. A common rookie maneuver is to put the meat over a fire that hasn’t burned down to coals. This exposes your meat to licking flames that will likely char the food beyond where it’s a good thing. And the smoke from freshly burning wood is more bitter than from coals. Both smoke and charring add flavor and complexity to meat, but too much charring or smoke and that’s all you taste. You want these flavors to be team players.
The choice of wood makes a big difference in how hot and quickly it burns, and how the smoke tastes. In general, hardwoods are better for cooking over than soft woods. Apple is perhaps the king of woods. It burns hot without too much flame, and has sweet smoke. Cherry is up there with apple. Alder burns more quickly and with less heat, but has good flavor.
Assuming you’re using wood of roughly two-inch diameter, a good rule of thumb when cooking over wood is to start the fire about 45 minutes before you want to cook. When the wood burns down to coals, spread them evenly under your grill grate and wait for them to cover over with ash.
While the fire is burning its way down to coals, salt a room temperature steak, and let it sit.
The grill should be three to four inches above the coals. You should be able to hold your hand at grill level for about two seconds before the heat forces it away. Grease the grill with a piece of fat or oil. The meat should sizzle softly when you set it down. After five minutes rotate the steak 90 degrees to make a crosshatch pattern. After four more minutes turn over the steak and repeat the process, turning it 90 degrees after five minutes. After that turning, an inch and a half thick steak will need roughly another two minutes to be medium rare inside. (or take away the guesswork by using the Halfsies technique).