There are many shops and Web Sites where you can buy some objects or pieces of forniture to make your work space more comfortable and so, more healthy.
If you are a long time using the keyboard or the typewriter, you should buy a special pad to put on your wrists.
There are many classes and sizes of mouses, there are mouses with ergonomic forms, but I don´t advise it you, because normally you can not change the hand to use it. You should buy the correct size for the size of yuor hand, so your fingers can be more relaxed.
To avoid pain and hurt in your neck, the monitor of your computer sholud be at the same heigth and opposite of your eyes, so you will not need to turn or to lower your head.
The desk should be spacious, but if you have some file cabinet I advice you to put it far to the desk or in other room, so when you need same document, you should have a little break to search it and strech your legs.
The most important piece of forniture of your work place is the chair. It should have a correct heigth and a correct position in its back, so you will avoid pains and hurt in arms and shoulders and in your back.
2.- This is a simple exercise that you can be when you are working at your computer for long time. Strech your arms and move your wrists doing circles, one minute for the right and other minute for the left, before in the same position open and close your hands and strech your fingers for other minute and at the same time you can do circles with your arms. Repeat this exercise every two or three hours.