Quick heat of hot oil really seals in the delicate flavor of fish, and if cooked properly (not too long) it keeps fish moist and tender. Batter dipped, dredged in seasoned flour or cornmeal, fried fish is as down-home as it gets.
I generally prefer peanut oil for deep frying, as it has a high flash point (temperature at which it ignites) and a flavor that is compatible with many foods. My second choice would be canola. Neither contains trans-fat, and both are unsaturated.
Fry in the heaviest straight sided pot you have. Cast iron is best, but anything that holds heat evenly will work. Be sure to point the handles toward the wall so there are no unfortunate accidents.
Whenever you are deep fat frying, it is important to regulate the oils temperature. That does not necessarily mean you must continually check a thermometer (I do not always trust thermometers). It does mean you must use your eyes and watch how fast the food is cooking.
Browning should be gradual. If the food begins to darken too quickly, turn down the flame and let the oil cool a bit. If the oil is not hot enough the food will soak it up, making your lunch greasy rather than crispy. Test the oil by dropping in a small bit of food. Oil at 350-375˚F will cause the food to immediately begin sizzling.
Brown on all sides, then drain properly before serving. The most efficient way to do this is with paper towels. Let the food drain on a stack of towels for 3-5 minutes before salting and serving. Remember to properly ventilate you kitchen, as frying fills the vicinity with that deep-fryer smell.
In decades past, fried fish vendors would cool their oil by dropping in buckets of cool sliced potatoes then they’d give away these “chips” to hungry passers by. What’s a chip? In England it’s a French Fried potato. Also in England, a potato chip is a potato crisp, and a cookie is a biscuit, a restroom is a WC and an elevator is a lift. Now you can travel to England free from humiliation … unless you insist on wearing your “I’m With Stupid” t-shirt. Then you’re on your own.