blog - How do I write a proper cover letter?

I'm an engineer with a fair knowledge of the English language. I can converse with people in English and write as well, but now I'm interested in learning to write cover letters and blogs. I see plenty of books on writing letters in different ways; however, I am still left with the following questions:

1. In what format can I write a cover letter?


2. Can I include technical terms in a cover letter?


3. Are cover letters sent through email differently than written letters?