Combine mustard, soy sauce, brown sugar, olive oil, ginger and garlic.
Whisk to combine.
Pour half of marinade over salmon and reserve the remainder.
Refrigerate fish in marinade for 10 minutes.
Remove fish from marinade and place skin side down on hot grill for 4 minutes.
Carefully flip fish and cook an additional 4 minutes.
Remove from grill, brush with reserved marinade and allow to rest for 8 - 10 minutes. Tip: I like to add about a tablespoon of Ponzu sauce to the reserved marinade. The sauce is wonderful drizzled over rice and veggies as well.