Enable/Disable read receipts.
Enabling read receipts means that the person you text can see when you've read their text message. This, obviously, has pros (transparency) and cons (you look like a jerk for not responding right away).
Open the Settings app, select Messages, and slide to enable or disable Send Read Receipts. Once it is enabled, the receipt will say "Read [time here]" beneath your latest text.
Photo: Nicole Nguyen