I'm not touching my index cards for my NaNoWriMo novel Dirty Pop till just one week before NaNo begins. But that doesn't mean I can't do some Internet research on the pop culture world in which main girl Charlie is trying to make her mark in.
First of all, there's the behind-the-scenes stuff that's going to be the tricky part: managers, crew, labels, legal stuff, etc. What you see on MTV or YouTube has a huge infrastructure behind it, and it needs to be part of the story.
Second: fashion. That's always been difficult for me to imagine, much less draw. In the non-Disney pop music world Charlie is trying to break into, it's important to have the right style — and right now that style tends to be a cross between the outrageous and the science-fictional.
Third: What real-life pop-cultural figures do I want to loosely base characters on? No, there won't be any roman à clef type stuff with thinly disguised real-life characters; my imagination is too powerful and strange for that. Knowing as well as I do how I work, I'm likely to mix, match, and mutate characters till they only vaguely resemble their real-life inspirations. Case in point: Charlie's mother Drusilla, a major villain in Bad Company and Black Science as well as Dirty Pop. As a New Age cult guru, I threw together at least half a dozen real-life cult matriarchs into the blender and set it to "puree". Dru has elements of JZ Knight (of Ramtha fame), Elizabeth Clare Prophet, Sylvia Browne, and my family's ex-guru from the late 1970s and early '80s, along with the fictional character Erica Kane (from the soap opera All My Children). (My suggested casting for the role: Cate Blanchett, unless it's Meryl Streep in full "Nuclear Wintour" mode.) This is the kind of character mashup I have in mind.
A good idea to keep in mind is that sometimes even the most frivolous pop-cultural confection needs some intensive research, even if it doesn't need quite the research that a political thriller about an evil military corporation that invades America needs. Of course, it shouldn't be overdone; that way lies procrastination...