What is the proper way to prevent widows/orphans/runts in Indesign?

Thanks, everyone! I thought I was quite versed in Indesign, but apparently, I am unfamiliar with GREP. Would you mind breaking down the concept and how it works like I am a 7 year old? I quickly Googled it and I am a bit lost. I know it sounds bad but I have recently written off paragraph styles because an intern once set up a document with the language set to Burmese... as it turns out, once you apply it then it is impossible to change and spell check did not work for a 600 page document. I am a little weary of automated processes in Indesign and want to make sure I don't make any mistakes that cause heartache later...

Thanks!

I suggest the "All of the Above" opinion, with one caveat.

1) Robert directs you to a post from Eugene suggesting a GREP find-and-replace. I often do it that way, but more often I do as Robert suggests and build it into a body text paragraph style as a GREP style. At other times I will do a find&replace to add non-breaking spaces between the last word and the second-to-last word in a given body text paragraph style. 

2) Dave suggests adjusting your hyphenation settings as well, which when set correctly can really improve your rag and minimize runts. His settings look almost exactly like my own.

3) I will often increase or reduce tracking by a few points, in addition to maybe tweaking the kerning, in addition to maybe a percent of glyph distortion in the Justification dialog (typically frowned upon, around here), while I'm reducing reducing inter-word spacing by a few percent.

4) I try very hard to avoid soft returns, but every once in a while one is necessary.

5) Similarly I try to avoid increasing or decreasing the width of a frame in order to affect the rag.

6) But in the final analysis, these are all just tools, and what you really need to do is what James suggests; you need to set up your tooling, then you need to ride the lines, looking at the rag of every paragraph in your document, and be ready to use any of the tools at your disposal in your efforts to create an aesthetically pleasing rag. 

But: I never use a hard return, as I'm usually using a paragraph style with some kind of defined indent or paragraph spacing. So I don't suggest getting in this habit.

An aside about terminology: The terms "widow" and "orphan" are generally accepted to refer to lines of text which are either the first lines of paragraphs left behind on the previous spread, or last lines of paragraphs that get pushed by themselves to the next spread. These are the terms found in Bringhurst's Elements of Typographic Style. Many years ago (like, maybe 20 years ago?) we had a thread here where someone posted "What do you call it when someone leaves one word by iteslf on the last line of a paragraph? I see people calling them widows or orphans, but that terminology is incorrect, c.f. Bringhurst." So in that thread, the term "runt" was suggested, and ever since I've seen that terminology spreading throughout the Internet. However, the term "runt" never appears in Bringhurst.

You know what does appear frequently, all the way throughout the Elements of Typographic Style, though? Runts. They appear frequently, in any edition of the Elements that I've looked at. I guess he didn't think they were something to avoid? 

Short line endings are not Widows or Orphans--they are paragraph issues. Some people call them Widows, so I tend to call them "Line Widows". 

This is what I do in my main Body style to prevent short endings:

I adjust the number depending on the column width used. If the character count hits mid-word, it still has to follow my hyphenation settings. 

The techniques to minimize/fix them is one thing; that link will give you all the basics. But eliminating such althogether is down to diligence by the designer. Not every detail can be automated or fixed by a feature.

Please check this thread: 

https://community.adobe.com/t5/indesign-discussions/does-it-matter-if-my-book-layout-has-runts/m-p/15091197#M605897 

But do it as a GREP Style.