If you have experienced professional or having any skill. You can earn a good living as technical writer.

Technical writing donot need to pass any college exam. Any one who can read and write good language can become Technical Writer.

But If you planning to write technical book then it is good thing to first learn the basic principles about the procedures of that instrument.

For quick summary about technical writer visit:

http://technicalwriter-nigam.
blogspot.com.

In my blog I summarize technical writer introduction.