We just had a very interesting discussion in the Ask the Nature Editor Forum about scientific writing. Most people agreed that the quality of the writing in the end doesn't really influence the decision to accept or reject a paper. But good writing, especially in the first paragraph, certainly helps.
But what is good scientific writing? Two weeks ago I suggested a few good books on the subject in a blog post. Once you have written the paper using the advice in these books, you can use a number of tools to measure the readability of your paper.
Flesch Reading Ease Score:
206.835 - 1.015 x ASL - 84.6 x ASW
ASL is average sentence length and ASW is average number of syllables per word. The Flesch Reading Ease Score can be between 0 and 100, 100 being the most difficult.
The Flesch-Kincaid Grade Level Test is similar, but rates the text on a U.S. school grade level. Both Flesch scores are built into recent versions of Microsoft Word or you could use the Open Source application Flesh. Flesh is much easier to use than the Microsoft Word tool and will also open PDF files. Try to rewrite your manuscript if your Flesch Reading Ease Score is too low, e.g. below 30.
Readability is important not only for manuscripts. Informed consent forms for patients wishing to participate in clinical trials in Medicine are often difficult to read. And a perspective article by Celeste Condit in the current Nature Reviews Genetics talks about How geneticists can help reporters to get their story right. She points out the importance of readability to communicate often highly technical material to lay people.