The key to great Carne Asada is all about the marinade. I usually make mine in a simple bowl, mixing the olive oil, lime juice, garlic, chili powder, cumin, salt, and pepper. Give it a little stir, then add in the steak. Let it marinate for at least 15 minutes, or longer if you have the time. The longer it sits, the more flavorful the meat will be, but trust me, even a short soak makes a huge difference.