I don't care what anyone says, you can screw up how well something is cooked, but if you have a solid marinade, you can often recover from over cooking a perfectly good piece of meat-within reason.
FRUITY: for seafood, poultry, pork tenderloin:
-mango or apricot nectar
-orange juice
-rice wine vinegar (not seasoned)
-minimum 4 cloves garlic, crushed
-honey
-hint of cumin
-hint of cayenne
-soy sauce
Marinate four hours or overnight, then grill. Some of this marinade can be reserved (reserve a portion BEFORE marinating poultry, meat, or fish) and reduced for use as a sauce.
SAVORY: For beef, lamb, or pork
-red wine
-red wine vinegar
-unsweetened cherry or cranberry juice
-soy sauce
-worcestershire sauce
-sprigs of rosemary
-minimum 4 cloves garlic, crushed
-black pepper
-hint of cumin
SWEET AND RICH: For lamb
-unsweetened cherry or cranberry juice
-orange juice
-rice wine vinegar
-honey
-minimum 4 cloves garlic, crushed
-hint of cumin
-soy sauce
-coriander
SOUTHWESTERN: beef, pork, chicken, shrimp, lamb
-lime juice
-pineapple juice
-rice wine vinegar
-garlic
-cumin
-cinnamon
-ancho or chipotle chili powder (be careful, these are spicy)
-fresh cilantro, chopped
METRO INDIAN: chicken, lamb, pork, seafood
-greek yogurt
-major greys mango chutney
-curry powder
-honey
-garlic
-orange juice
-rice wine vinegar
-black pepper