Basic advice: Don't crowd the pan, you want to err on the side of too few potatoes in the pan. (This is doubly true if you're making extra crispy hash browns) And don't flip the potatoes too often, otherwise they won't get very crispy / Maillardy.
Microwaving before frying drives off moisture, which reduces overall cooking time and allows more hash browns to fit in the pan. This is optional, however.
Whenever you're frying something, use a fish spatula, because it lets the oil quickly drain off the food.
Individual steps:
Put the hash browns in a very large microwave-safe bowl (one that's wider than it is high) or microwave-safe baking dish. Drizzle ~2 tbsp oil over the hash browns. Toss them a bit to evenly coat everything with oil.
This keeps the hash browns from sticking together. If you like clumpy hash browns, skip this step.
It doesn't have to be a bowl, you can get away with a plate, but flipping the potatoes becomes much harder.
Microwave them for ~3 minutes (~5 minutes if they're frozen). Take them out every ~30 seconds, wait 5-10 seconds until they stop steaming. Flip the potatoes so the bottom side can release steam too. Once they're done steaming, return them to the microwave and resume heating.
The goal is to reduce moisture in the potatoes. Moisture prevents crispy Maillard reactions from happening, and microwaves specifically target water molecules.
This reduces the overall cooking time somewhat, but the biggest benefit is that you can fit more hash browns in the pan without overcrowding them, since the potatoes shrink during this step.
Heat a pan at medium, fill it with oil (~4 tbsp?), and move the hash browns into the pan. Pro-tip: USE A FISH SPATULA, it helps to strain the excess oil off the potatoes. A silicone-lined fish spatula is fine, if you're using a non-stick pan.
A few minutes before they're done, add ground pepper so it gets bloomed. I traditionally add salt here too, but it doesn't matter when.
If you're aiming for hash browns that are extremely crispy and very browned, start your heat at low-medium instead. This gives you a little more control that you need to hit the "browned without being burnt" target.
Also, avoid having too little oil in the pan. If you notice the hash browns only crisping on the very bottom, then you need to add more oil, otherwise that part of the hash brown will get over-cooked. You want to be always cooking at least the bottom half of each hash brown (this depends on how finely the hash browns are cut), in order to ensure a more even amount of cooking.