I usually just edit pages for minor grammatical, spelling, and punctuation errors, whenever I happen to notice them. I occasionally patrol recent changes, and remove obvious vandalism. But as far as I can tell, I don't make changes just to reflect my personal tastes.
There are also a few topics in which I have a special interest and I may edit content on pages related to these topics. In particular, if I am aware of recent research which allows an article to be updated, I will add the information.