Adding Space Between Paragraphs, Not Lines
I'm using the Baseline Grid to keep the lines aligned between verso/recto pages, but with my keep options turned off I get orphaned/widowed lines every once in a while. Turning on Keep Options (1 line in front, 2 at end) fixes the orphan/widow problem, but makes it so that every once in a while I get one page one or two lines shorter than than the one next to it. While the orphans & widows are typographically annoying, I think the uneven page endings look careless and unprofessional (especially when the difference is two lines).
There's a third option that I tried: If I set the master text frames to be "vertically justified", the top and bottom lines always line up, and I can set the keep options to get rid of widows and orphans. The problem with this is that it ignores the leading and gives uneven baselines across the spread, which looks odd when printed out.
So my question is this: What do I do?
Well, you know that great old one-liner: "Fast, good, or cheap: pick any two"? It's kind of like that. While there is no great answer to Getting It All, there is at least one thing you should look at: The Paragraph Spacing Limit field in the Text Frame Options dialog box (Object > Text Frame Options, or press Command/Ctrl-B).
When Paragraph Spacing Limit is set to zero, and you have the Vertical Justification alignment set to Justified, InDesign adds the same amount of space between each line of text in the frame in order to "bottom it out." That is, the vertical justification completely ignores all your leading values. But when you increase this value, you're telling InDesign that you can add some extra space between each paragraph, which makes changing the leading less necessary.
I almost always increase this value to an inch or more, so that InDesign puts all its effort into adding space between paragraphs and doesn't change my leading at all.
But as you can probably guess, this still doesn't do anything for aligning your baselines across the spread. So what do you do? I suggest rewriting a few lines to make it fit better, or just delete all the verbs and see if that helps. ;) No, seriously, if there is a better answer, I don't know of it and I'll be curious to see what solutions readers propose below.
Ultimately, it would be cool if Adobe InDesign implemented a "make it all bottom out" feature, which might use a smarter form of the Paragraph Composer to figure out the proper spacing across one or more pages. Or perhaps a smarter vertical justification that would add space more cleverly between paragraphs. (Brad Walrod has long been a proponent of someone writing an InDesign equivalent of the old ProVJ XTension. I've talked with some plug-in developers and I hope we'll see something like this before too long.)