In a small bowl whisk together balsamic vinegar, soy sauce and freshly minced garlic.
In a medium sized shallow dish or ziploc bag, add your raw steak and marinade. Mix so that the steak is fully coated in the marinade.
For best results, marinate for at least 20 minutes in the fridge (not room temperature for food safety!) and then prepare your marinated steak however you like to and to your preferred level of doneness.