Sometimes you can have a conversation in Gmail that has dozens and dozens of messages… but only a select few are really important to you. How do you make it easy to find those when you look for them later?
When I first open the conversation in my in-box, the starred messages are already expanded for me. Easy to keep track of important messages this way!
To add a star to any message, just click the star icon! (Another click removes the star.) That’s all there is to it.
If you’d like to have more options besides star and no-star, open your mail settings (gear icon at top right -> mail settings) and choose among the various “Stars” options among the extended sets, in the first tab of settings. Easy!
If you have keyboard shortcuts enabled, you can type N and P to move the cursor to the message of interest, and then type S to toggle the star (or to rotate through all the available stars if you make more than one available).