Don't overthink or overcook. Always serve it rare, including and especially the heart and only medium rare for the liver. Marinating is almost unnecessary unless you're doing roasts and even then, not really necessary. Use simple fresh
ingredients - fresh garlic, sea salt, freshly ground pepper, onions, peppers, olive oil, butter, good red wine, and use the BBQ grill a lot. And if you didn't get it the first time, don't overcook it. Then the next time you cook it, cook it less. If it's tough, it's your fault.