1. Pluck a strand, drop it in a bowl of tepid water, and give the strand a light nudge with your finger. If the strand floats, your hair is in fine shape. If the strand sinks, it’s a sign your hair could use some tender loving care in the way of trims, gentle handling, pre-shampoo treatments, a gentler shampoo, deep-conditioning treatments and, yes, a moratorium on the heat-styling.

2. Yank out a strand and examine it under a magnifying glass. If you see signs of fraying or splitting, you need to take the action.