We like to grill ours. I used to beat the heck out of it with a meat tenderizer & then marinate in Newman's Own Balsamic Viniagrette for a couple hours. (Don't know how long to grill each side as DH does that. ) When it's too cold out to grill (or we run out of propane, we broil.)
Ever since our stay at Animal Kingdom Lodge, however, we only make this one:
FLANK STEAK MARINADE(or any kind of steak
For 1½ lb steak
½ c Ginger
¼ c Garlic
¼ c Sugar
½ Tbl Cardamom, ground
1 Tbl Coriander, ground
½ Tbl Turmeric, ground
1 Tbl Thyme
½ Tbl Crushed Pepper
1 Tbl Worcestershire Sauce
½ c Soy Sauce, low sodium
Mix all ingredients in a large bowl. Add steak & marinate for 4 to 24 hours. (The longer the better, but it's really tasty after only 4!)
Note: Its very thick, not like a normal marinade.
I like to use a seasoning called Monteray Steak Seasoning. Many different companies make it and you can get it in most spice sections of the grocery store. Its a little peppery, spicy taste.