There's a great book that attacks dense writing and how to fix it [1]. It is a quick read.
For example the author takes this sentence:
Pelicans may also be vulnerable to direct oiling, but the lack of mortality data despite numerous spills in areas frequented by the species suggests that it practices avoidance.
... and turns it into this:
Pelicans seem to avoid oil spills by avoiding the oil.
This sentence is shorter, but it also contains less information. I would say the 75% reduction in sentence length comes with a 66% reduction in contained information.
Ha, spoken like a true engineer. However, if the point of writing the sentence is not data storage but communication, then a long, convoluted sentence can be less successful than a shorter, more readable one. Maybe I picked a bad example. Here is another one:
Before:
Perception is the process of extracting information from stimulation emanating from objects, places, and events in the world around us.
After:
Perception extracts information from the outside world.
Yes, the first is more specific and more detailed, but the "outside world" includes things like objects and places and doesn't add much to the gist. The second one is certainly more readable.
I often see writing (especally from engineers) that is meant to be informative that is overwhelmed with irrelevant information. That is difficult to parse. Sometimes you want to pick out just a few relevant facts and leave out anything that isn't strictly needed so your audience understands the point.
It depends on your audience and you reason for writing what sort of information is needed and what is not needed. Its not an easy skill.
For example the author takes this sentence:
Pelicans may also be vulnerable to direct oiling, but the lack of mortality data despite numerous spills in areas frequented by the species suggests that it practices avoidance.
... and turns it into this:
Pelicans seem to avoid oil spills by avoiding the oil.
[1] "Revising Prose", Richard Lanham. http://www.amazon.com/gp/product/0321441699/ref=pd_lpo_sbs_d...