Ergonomics are really important. As well as helping keep your wrists healthy, they allow you to type faster and more accurately.
Did you know QWERTY isn't the most efficient type of keyboard? DVORAK keyboards need less travel time, and thus less effort to use, for most words. It's a big ask to relearn a keyboard, especially for a touch typist so making the most of a QWERTY keyboard is a must.
For best ergonomics, the general advice is to have the keyboard directly in front of you, with your elbows at 100 to 110 degrees (i.e. open rather than closed). Ideally, you can adjust your desk / chair to accommodate that. Keyboard trays help here as they'll be in a lower position than the monitor forcing an open elbow stance.
Having your keyboard directly in front of you doesn't mean central on the desk. Most authors use the letters much more than the number pad, so having the keyboard a little to the right is ideal. The idea here is to keep the wrists straight while typing.
Of course, a great deal of comfort comes from the keyboard. You can get all styles of keyboards these days including some articulated, some split in two and some with funky 'ergonomic' designs. We've got bog standard flat boards, but prefer to use mechanical switches to type with to force more ergonomic uses.
Unlike scissor switches, mechanical keyboards have full spring loaded systems, typically an 'MX Cherry' design. If you had a keyboard pre 1990, you probably had a mechanical one. These come in various flavours which are labelled by colour - black, brown, blue, red being the most common. The difference is usually twofold:
1. The force required to actuate
2. The actuation point/ distance.
i.e how hard is it to press a key, and how far down has it got to go before the keystroke is registered. Shorter travel times mean quick typing, and less force means less fatigure. MX Reds are the lightest keys, and actuate very easily so you only need to tap a key, rather than fully depress it.
Cherry MX Blue keyboards are the typical pro typist choice as they have a clicky audible feedback element to them, are clean to type on requiring a little more force than Red keys (which are designed for gaming) but are still mechanical in nature.
Mechanical keyboards also last for a lifetime - 50 million key presses. So the initial investment is worth it in the long term. Think £70/$100 for a basic one.
I quite like Filco Majestouch 2 keyboards for typing, but QPAD & Corsair make some great entry level mechanical keyboards too. I'd shy away from the gaming focussed boards - they tend to have a bit of a gaming premium added. Most typists don't need n-key rollover (which lets you hit all the keys at once and have them all register) nor is a back light necessary (but can be handy if you like a dark quiet room to type in). Media keys, ninja printing and other options are all to taste but the variety of such a simple accessory is simply astounding.
So, what do you guys use?