Possibly one of my favorite BBQ dinners as a child was the marinated flank steak my mom made. I kid you not, nobody has EVER said they did not like this recipe!
3/4 C vegetable oil
1/4 C soy sauce
1/4 C honey
1 1/2 t ground ginger (if you have it, fresh ginger is even better)
2 T vinegar
2 T chopped green onion
4 cloved minced garlic
Mix all above and marinate flank steaks at least overnight. I usually mix in a gallon-sized Ziplock baggie, add the steak, and let it sit for 2-3 days.