I tend to write about whatever interests me. Still, novels like Nick & Norah's Infinite Playlist are extremely popular because they are geared towards their audience, even though there are some popular references in it. If I do use references, I use ones that are very popular and won't seem to die out so soon. For example, one of Meg Cabot's novels features a main character that is obsessed with Gwen Stefani. Almost everyone knows who she is, so that's okay.