By adding members to your Favourites, it makes it easy to find them again in an easy-to-manage (and strictly confidential) list. If they come online at the same time as you, you will receive an on-screen notification in case you wish to start a chat with them instantly. So if someone catches your eye, hit the 'star icon' link on their profile page to include them in your favourites list (you must be logged in to RSVP). To remove them from your Favourites list just click on the star again to unhighlight.
To find your Favourites list, select Home from the main menu then Favourites from your sub-menu.