Turning on this Composition preference enables you to see instantly where you (or anyone else in your workgroup) have applied custom tracking, most likely for the purpose of tracking back a line to fix widows and orphans or to save space. This can be enormously beneficial if you suspect that one of your (less-typographically sensitive) colleagues has been using tracking a bit too zealously, or if the text content has been revised and the tracking that you had previously (reluctantly) applied is now no longer needed.
#9 Kerning and Tracking Increments
Speaking of kerning and tracking, InDesign’s kerning and tracking is based upon a 1000 em unit square, and you can adjust the spacing between characters in increments as small as 1/1000 of an em (an em is relative to the point size of the type: for example, with 24-point type, an em is 24 points). On a cautionary note, I recommend that you change the factory default for the kerning and tracking increment from 20 to no more than 5. This determines how much space is removed (or added) when you use the Option/Alt+left arrow/right arrow keyboard shortcut to apply tracking or kerning.
#10 The Hyphenation Slider
Many typographic choices are a trade-off and none more so than determining the number of hyphens in your body text. The more hyphens, the better the word spacing, but too many hyphens can make for broken reading. Based upon your personal threshold for hyphens—some people hate them, others find them useful little helpers—you can decide upon how many hyphens to allow by using the Hyphenation slider. Also, be sure to uncheck Hyphenate Last Word: a simple way to prevent your paragraphs from ending on a single syllable. Who would ever want that?