I usually make my fish and chips from haddock, though most white fish works. Traditionally it's made from cod. I usually get frozen haddock which conveniently comes in a bag with two separate vacuum sealed packages, and one package is exactly one serving. I defrost the fish, still sealed in its vacuum bag, in cold water, for an hour or two.
When it's time to cook the first step is to make a batch of fresh homemade tartar sauce. It's easier than it sounds:
minced shallot (can substitute onion)
1 tbsp. pickle relish
2-3 tbsp. mayonnaise
salt
pepper
It should probably have a little lemon juice in it, but I hate to juice a lemon for 1 tsp. of lemon juice, and I find that it makes it kind of watery. So I usually just leave it out.
Heat up your oil to 360°F. I use non-specific "vegetable oil." I have a serious deep fryer, but lately I've just been using 1 quart of oil in a pot on my induction hot plate. It works perfectly every time, and cleanup is much easier.
You can just take the fish as-is for regular fish and chips. If it's particularly large, cutting it in half is probably not a bad idea. But lately I've been cutting them into finger/fish stick form. They're easier to eat, cook and dip in the tartar sauce that way. And you get a more batter per serving. Season with salt, pepper, granulated garlic and a cayenne pepper.
Prepare a batch of beer batter. Beat one egg in a bowl. Then discard half of the egg. This is kind of weird, but you really only need half an egg. Add 3 oz. of beer and beat lightly to combine. Then beat in 1/4 cup all-purpose flour. That's it!
Dredge the fish in flour, then dip in the beer batter, and deep fry for 3 minutes. The stick format cooks a little faster. If you're using a thick, full-sized piece of cod it could take 4 minutes or more.
Remove the fish from the oil and salt.
Lately I've been lazy and using frozen French fries instead of making my homemade steak fries. Aside from the general pain of cutting fries and par-cooking them at 270°F first, it's just so convenient to take 3.5 to 4.0 oz. of frozen French fries and just toss them into the fryer for 2 minutes for perfect French fries.
Remove the fries from the oil, salt, and season with fresh-ground black pepper, cayenne pepper and granulated garlic.
This is what it looks like as regular fish and chips instead of fish sticks and chips: