It's hard to think of a cut of meat that is more conducive to cooking for a crowd than flank steak. It's got a robust, beefy flavor and a pleasantly tender texture with a bit of good chew. It comes in large, regular shapes that make cooking, slicing, and serving easy, and they're just thin enough that they'll cook through in a matter of minutes, but just thick enough that you can still get a nice, medium-rare center.
1) Choose a thick cut of meat. Generally, the thicker the better, especially if you like steak that has a perfectly brown, crispy outside and a juicy, pink center. See if you can't get steak that's 1 1/4" or 1 1/2" thick. If a single cut is too large for an individual, it's perfectly acceptable to share the steak with someone else or even to save it for later. Why is thicker steak better than thinner steak? Thicker steak takes longer to cook through than thinner steak. With thinner steak, you're risking overcooking the steak in the center by giving them a nice crust on the outside. With thicker steak, you can cook the outside for longer without worrying about overcooking the steak in the center. Especially when grilling, where high heat is often used, thin steaks become a problem. Best to choose a thicker cut, especially if you can't adjust the heat on the grill with a knob.
2) Season your steak liberally with salt at least 40 minutes before grilling. Salt draws moisture out from meat, which is an incredibly bad thing is you choose to salt right before you grill. Instead, apply the salt at least 40 minutes before grilling, and up to several days (yes, days!). What happens when you salt at least 40 minutes before grilling? The salt draws the moisture out of the meat, but with nowhere to go, the moisture eventually ends up seeping back into the newly tenderized meat. The longer you let the salt sit on the meat, the more tender it becomes and the more moisture it draws back in.
3) Allow the steak to come to room temperature before grilling. Steak that is room temperature cooks more evenly than steak that has recently been refrigerated and is still cold in the center. Steak that has been brought up to room temperature created a more evenly-cooked final product. Plus, you won't have to cook it as long on the grill.
4) For best results, choose a hardwood coal, such as mesquite, for your fuel. If you don't have a hardwood coal, you can also employ briquettes, but briquettes burn at lower temperatures for longer. (Hardwood coal burns at higher temperatures for shorter.) Instead of using lighter fluid, always use a coal chimney. If you don't have a natural-burning barbecue, don't fret. Gas is fine. Just don't expect the exquisite smokiness that's standard in natural-burning 'cues. Gas 'cues also don't get quite as hot as charcoal 'cues, meaning that you'll probably have to cook your steak for a tad longer.
5) Arrange the coals on the grill so that one half contains no coals and the other contains all the coals. This will create a hot side of the grill and a cool side of the grill. You'll be cooking primarily on the cool side of the grill to ensure a juicier, tastier steak.
6) Start the steak on the cool side of the grill, keeping the lid closed. Many grilling guides advise cooks to "seal in" the juices by searing the steak over high heat first. This is a myth. In fact, juices run out of the meat depending on what temperature you cook the meat to, not proportional to what temperature you cook the meat at. Searing the steak first cooks the outer layers to the point where they start to lose juices immediately. It also leaves the outer layer nearly fully cooked before you've really begun cooking the rest of the steak. In contrast, cooking the steak over indirect heat for longer periods cooks the whole steak while developing a nice crust (slowly). Then, when you're just about ready to take the steak off the grill, you can place it over direct heat and develop a golden brown crust, if necessary.
7) Flip often. Flipping often, especially if you're cooking over low heat, helps cook the meat more evenly. When flipping, be sure to use tongs or a spatula. Do not use a fork, as you will begin to lose juices.
8) Use a thermometer to tell you when you're done cooking. Sure, it's not real manly to use an electronic device to tell you when your steaks are done cooking, but it sure works. That's because you want to "peek" into the middle of the steak, which you can't really do by just looking. You can, however, use the finger test to determine whether your steak is done if you don't have a thermometer. 120° F (48.8° C) = Rare 130° F (54.4° C) = Medium rare 140° F (60° C) = Medium 150° F (65.5° C) = Medium well 160° F (71.1° C) = Well done
9) Sear the steak quickly about 15° F before it reaches its ideal temperature. If you've cooked it long and slow, it should already be well on its way to having a wonderful crust. Searing shouldn't take longer than one or two minutes on each side
10) About 5° F before it reaches its ideal temperature, take the steak from the grill and let it rest. It's very important to let your steak rest. Right after your steak has finished cooking, the muscle fibers on the outside are still relatively tight, which sends the juices toward the inside of the steak. If you cut it open right now, the juices — which are compacted in one small area — will leak all over the place, leaving you with a relatively dry steak. If, however, you let your steak rest before you cut into it, the muscle fibers relax and allow the juices to travel back through the rest of the steak. Instead of a hockey puck, you have a perfectly cooked steak.
11) Enjoy your steak with some summer fare. Why not accompany the steak with some potato salad, grilled zucchini, and homemade chips.