Writing Styles

MS Word can improve your Grammar and Writing Style significantly, and give you a Readability score for your work. Here's how to switch on the analysis tools. (From what I've seen, it's a much better indicator than the Fog Index). The following comes from my Technical Writing Course).
In MS Word, select menu > Tools > Options > Spelling and Grammar tab.
I recommend the following settings (from Office 2003, but look for similar if you have different version of Word).
Spelling: Put a tick next to the following:
Check spelling as you type.
Always suggest corrections.
Ignore Internet and file addresses.
Then in Grammar section:
Check grammar as you type.
Check grammar with spelling.
Show readability statistics.
Writing Style: Click on the drop-down and select Grammar and Style.
Click on the Settings button and you will probably find the defaults are OK, but clear any ticks that you are not happy about. (For example, I don't mind sentences beginning with And, But, etc. Plain English doctrine says It's OK to use these occasionally for impact or emphasis.)
Click OK and OK again to finish.
Word will then keep check on your grammar and writing style, as well as spelling. Remember, it provides indicators of what it thinks might be a problem area; often you can click "Ignore Once"; but sometimes it's accurate and most helpful.
Next, make sure (a) your default language settings are correct, and (b) the language set for the whole document is the same, or it won't work properly.
Then, when you finish your doc, do a final spell-check [F7] and deal with any suggested corrections. Then it will display a Readability Analysis of your document.
For good style, aim for Average Words per Sentence around 15-20. Passive Sentences, keep it low: maximum 20%, but aim for 10% or less.
Flesch Reading Ease aim for 60-70 for most readers; lower is more difficult.
Flesch Kincaid Grade level aim for 7 to 8; higher is more difficult.
If you have overseas readers whose first language is not English, remember to choose suitable vocabulary, and use no idiomatic expressions – they often don’t translate!
(Look in Word Help for "Kincaid" if you want details.)
Gradually you will develop a good writing style if you don't quite have it already. (This reply scores Passive Sentences 0, Flesch Reading Ease 66.1: right on target.)
Hope this is helpful.
Philip