Heat the oil to 375 degrees F., same as for pan frying. The only difference is you use enough oil to float the fish.
As long as you cook with low cholesterol oil, get it nice and hot, and take the fish out as soon as they're done, they won't taste like they've been soaking in oil.
Cut fillets into 3" pieces and place in cold water. Take fish out of the water, let some water drip off, and drop them into the plastic bag with the dry batter. Shake gently until throughly coated.
Open 1 package of Mr. Walleye Breading and Batter Mix and put in a bowl big enough to hold the batter, a can of beer or less, and a few fish pieces.
Mix the batter and beer until the batter is like thick soup. Add less or more beer based on how much breading mix you have.
With tongs or a fork, drop the coated pieces into the beer batter. Lift out of beef batter, let excess drip off and put into the hot oil.
The fish should come right up and float as they cook. Make sure the fish cooks thoroughly on both sides. Some flip over as they float in the oil, and others you may have to turn yourself. Turn the fish once. It doesn't take long until they're golden brown and done.