Basics for grilling fresh fish:

Rinse the fish with cold water and pat dry.
If desired, marinade the fish in the refrigerator for about 2 hours.
Season as desired.
Lightly grease foil or unheated grill rack.
Cooking time is 6 to 12 minutes per inch thickness.
Turn fish halfway through estimated time.
Grill the fish until it is just opaque throughout.
As a rule, shellfish cook faster than fin fish.