First make your batter. Our prefered recipe is as follows:
Mix the beer or soda water in slowly, whisking with a whisk or fork until you get a thick porridege consistency. Do not overwork the mixing of the batter, a few lumps will be fine. Overwork it and the batter will become tough. Leave for 2 hours to chill in the fridge covered if you have time, if not it will be fine.
The other ingredients you will need are:
Now get your fryer to 170 degrees. For ease if you have big fish pieces you may want to cut them into smaller pieces which are easier to handle and fit more easily into a home fryer. Now dip the fish a piece at a time into the seasoned flour until well covered. This will ensure the batter stick. Now dip the fish into the batter (I keep my batter in the mixing jug and lower it in by my fingers). Now lower slowly into the oil. If you drop it in, it will stick to the wire mesh of frying basket. It should now quickly float to the surface. Allow to cook for 2-3 minutes depending on thickness of the fish and then turn it so it cooks evenly. When the batter is deep golden in colour, remove to kitchen towel. If you are only cooking a couple of batches the first will stay hot while the 2nd batch cooks. If cooking more then preheat an oven to 100 degrees and place the cooked pieces on a wire rack. They should stay crisp but if the moisture in the oven causes them to go soggy then dip them back into the fryer for 1 minute before serving on the plate.
I normally have to cook 3-4 batches and then serve with chips which with 1 small home fryer can be done if you first cook all the chips and drain and keep in roasting tin on the side. Then cook the fish and pop in the oven as above. Then when your fryer is free again, refresh the chips in the oil for 1-2 minutes in batches, refresh the fish batter likewise if needed (with my oven usually not necessary) and serve it all up and it should still be piping hot!
One other tip! Occasionally no matter how hard you try the batter will break off or have slid off a small bit of the fish while cooking. When the side with the "hole" is up in the fryer just spoon a little batter from the jug over the whole then turn it back over after a minute or so to ensure it cooks through.