One of the things I do for a living is type. I transcribe videos for captioning on a daily basis which sometimes entails typing for most of the day. If you are someone who has to type a lot, this can lead to finger and wrist problems and even debilitating injuries such as carpal tunnel syndrome.

I have been typing heavily daily for almost four years now and have not had any problems other than fatigued fingers and wrists. Any pain that I have had has been short-lived and not ever prevented me from doing my work. Here are some things that I have used since the beginning to prevent injury that may can help you:

Use an Ergonomic Keyboard - Ergonomic keyboards are essential for someone who makes a living typing. They have a shape which is more comfortable to use such as a curved keyboard which is often split to more naturally position the wrist. I use the Microsoft 4000 mainly because of its price and availability (I wear one out every six months). But whichever one you use, choose carefully, because once you get your typing speed up past 70 words per minute on one keyboard, you won't want to change to a differently designed keyboard.
Use Wrist Support - I don't always use wrist support, but you can buy heavy wrist supports like this: Or you can use lighter wrist support like this: I like the latter, because of the comfort issue. The lighter wrist support such as a sweat band will help you with fatigue at the end of a long day of typing and most of the time you barely notice it. The heavier type of wrist support will be more useful if you are in some pain and think you may be on the verge of injury, but they do tend to be bothersome if you wear them for long periods of time.
Anti-Inflammatories and Glucosamine - One of the things about heavy typing is it can cause inflammation of the joints in your fingers and wrists. This can be countered with anti-inflammatory medications such as aspirin or ibuprofen. I personally take a baby aspirin every day to ward off inflammation and sometimes a heavier dosage if necessary. It also is supposed to help with warding off cardiovascular disease; so kill two birds with one stone. Glucosamine and chondroitin can also help in that they support the lubrication of joints. I like the supplements that have both along with vitamin D, and I think they have helped me a lot in maintaining my finger and wrist joints.
Stretching and Frequent Breaks - I find that stretching is most essential in the morning before I first begin typing, and it is when I do it the most. You want to do stretches of not only your hands, but your whole arm, as the tendons and ligaments involved in typing can be found throughout the hands and arms. I like to do stretches that involve pressing the hands either together or against something like the wall while stretching the fingers and wrists and pressing upwards with my whole arm. It's important to take breaks at least every 30 minutes or so and stretch a little. It makes a huge difference at the end of the day.
Change Typing Positions Frequently - I have a desk where I can stand, sit, and sometimes I even lay on the bed and type for periods of time. I have found this is one of the best ways to ward off any fatigue and pain not only of the hands and wrist, but also the neck and shoulders, which is another frequent area of pain for professional typists.

Many a typist's career has come to a sudden halt or ended because of serious injury, but if you are careful and conscientious, that injury can be prevented. It is possible if you are careful to type every day for your whole life, like I plan to do, and not have any major problems.