The Flank Steak is excellent for stir fry or "carne asada". Flank is often the better alternative to skirt steak when it comes to fajitas, shredded beef (ropa vieja) or similar dishes because of its texture.
Cook it at high temperatures and marinate it properly. It is a very tasty cut of meat thanks to its INTENSE beefy flavor.
Cutting the meat against the grain is the most important thing to remember when you're serving and eating it. The grain refers to the long strands of tough fibers that you can see running through the meat.