I found that the best way to avoid widows and orphans is setting penalties and using rubber lengths between paragraphs, for instance, \setlength{\parskip}{1pt plus 1pt minus 1pt}.
When I shared this piece of knowledge with the LaTeX Users Group, however, I was told that
[…] it's the default solution […] It is also disallowed by most publishers working to a grid or specifying type be set solid. It works best with a layout that allows or encourages space between non-indented paragraphs (like a business report).
Since then, I wonder how professional publishers who use LaTeX deal with pagination issues. Using \enlargethispage is another possibility, but just as awkward. And, well, if it can be done with Adobe InDesign, it certainly can be done with LaTeX (or ConTeXt etc.).
To sum up: what are the proper strategies, commands or settings one can use to accomplish industry-standard results when it comes to pagination?