What do each of the Signpost/Linking words & Phrases do?

Many of us foolishly object to taking courses in writing. University students going into business often think their secretaries will do their writing for them.This attitude shows a naïve faith in the role of their secretaries. Indeed, young business people seldom have private secretaries. Similarly, graduates taking up positions in technical or scientific fields may think that writing is something they seldom have to do. However, our notion that only poets and novelists have to write is unrealistic. For example, practising scientists and engineers say they spend half of their time writing papers and reports. Therefore, other things being equal, a person in any field who can express ideas clearly is sure to succeed.