Combine equal parts olive oil with an acidic liquid such as lime juice or balsamic vinegar to create a marinade. Add seasoning and flavoring to your taste, such as salt, pepper and minced garlic. Pour the mixture into a resealable bag.

Add the fillets to the bag of marinade and place in the refrigerator for about 30 minutes to 1 hour, turning the bag over halfway through.

Submerge flavored wood chips in a container of water to soak for about 30 minutes and add charcoal to the bottom of your smoker grill. Fill the water pan in your smoker to the line indicated. You'll want to use a light fruitwood to smoke your haddock, such as an apple or peach wood that won't overpower the delicate fish flavor. Avoid using mesquite or hickory chips, which are far too strong for this fish.

Light the charcoal and bring the heat to between 200 and 225 degrees Fahrenheit, using the vents to adjust the temperature. When the coals start to ashen, place the soaked wood chips on top and close the smoker.

Place the haddock on squares of aluminum foil cut to fit each fillet. Put them on the center racks of your smoker and close the lid. Let the haddock smoke for about an hour to 90 minutes, or until the fillets are no longer opaque and the flesh flakes easily with a fork. The fish must also reach an internal temperature of 145 F, which you can check with a meat thermometer. Serve hot out of the smoker.