I type QWERTY at 90 words per minute. Based on the benchmarks in TypingTest, this is relatively fast. The average typing speed is said to be around 35~40 WPM.
I was able to achieve such speeds through touch typing. It is a typing style that doesn't use sight to find the keys but rather muscle memory.
The fingers should always be in the home row keys when idle. The small bumps on certain keys of the home row help typists return their fingers to the home row for touch typing. Each finger is assigned a set of keys to press.
There are already many articles regarding this topic. The principle is to always use the correct finger when hitting the letter key.
How I learned it
In my early years in grade school (early 2000s), my dad encouraged me to learn to "type properly," which he refers to as the touch typing method. However, we didn't have a computer at home, and the only time I can use a computer is at school.
I familiarized the keys through a keyboard drawn on an illustration board. It wasn't enough - to be good at something physically done, you need to apply and practice it.
Eventually, my dad bought me a video game keyboard console for typing practice, which has typing mini-games built-in. When the game difficulty rises, the player must hit the right keys faster and accurately. It is not like pressing a button or two on a PSOne controller; you need to find and press the required letters on a slab with more than 50 buttons.
The typing video games allowed me to practice and apply touch typing because I wanted to achieve high scores. It helped me develop the habits for touch typing at an early age.
Use a good keyboard
The keyboard you use affects your typing performance and hand. As of writing, I'm using a Kingston HyperX mechanical keyboard with Cherry MX red switches. The Cherry MX red is silent and doesn't bother my co-workers much. It's very comfortable to use, and it doesn't hurt my wrists much.
Laptop keyboards are not advisable if you're going to type for long periods. I find MacBook (especially the one on the 2016 model and later) keyboards terrible. The keyboard on my ThinkPad X220 is better than the one on my MacBook Pro 2016, but I still experience wrist pain when using it for prolonged periods. I recommend using an external keyboard.
I recommend keyboards with mechanical switches. However, their expensive price tag can be a turn-off to most people.
I am yet to experience using an ergonomic keyboard. I plan to buy one soon.