David Rosen is only in his mid-30s, but already he has racked up careers as an advertising creative director, a novelist, and a TV writer. Now he’s packed the equivalent of a lifetime’s worth of informational interviews into a book called What’s That Job and How the Hell Do I Get It?

In it, Rosen offers intimate profiles of and insider advice about jobs like fashion designer (do an internship, and remember that you will put in many, many hours before becoming the next Karl Lagerfeld) and private investigator (whether a job is done well or poorly, you’ll rarely make your clients happy). Rosen spoke with U.S. News about cool jobs and his own career.

Were you trying to dispel common misconceptions about dream jobs with this book?
I was working in advertising at the time, and I was getting a lot of calls from parents’ friends’ kids who were like, “I really want to do what you do. What exactly is it you do?” I had a lot of what I call over-a-beer conversations where I started to realize that what people wanted to know [about jobs] was more than just how much money you make or things you can Google. They wanted to know the lifestyle. Because I think people see how happy or unhappy their parents are, putting on a tie every day, and they start to have those broader questions—not just, is this my dream job, but, what is my life going to be like?

I wasn’t as much trying to dispel [misconceptions] about the jobs and find counterintuitive things but more really just trying to get the details that people don’t ever really talk about.

What were some things you learned that surprised you?
When I interviewed private investigators, they were like: Oh, man, the week of Valentine’s Day [is busy]. Valentine’s Day itself is not a busy day, but the weeks of, before, and after are. Then I thought, with the whole Eliot Spitzer thing, they nailed it. Because apparently, you’re with your spouse the whole Valentine’s Day, but the day before and the day after is date night.

If you’re going to interview for a publicist’s job and your interview is in the afternoon, watch Good Morning America . See who’s on. Then Google them and find out who their publicists are. Maybe it’s where you’re interviewing. When you get there, drop the “Hey, great job getting [the guest] on the show.” It makes perfect sense, but I wouldn’t have thought of it.

Are some jobs unexpectedly difficult?
Well, there were definitely jobs that I was like: I could never do that. Like a doula [someone who helps a woman through labor and childbirth]. The job of band manager was really interesting because you think of it being this rock-and-roll lifestyle, and, to an extent, it is. You’re on the private planes and all that stuff. But at the same time, you’re the chaperon of the rock-and-roll lifestyle. You want to have fun with everyone, but the next day, you’re the guy or gal who’s like: We have a show tonight; let’s get it together.

The job profiles are obviously useful for college students and recent grads, but which jobs would make good second careers?
Real estate is definitely a second career that people go into. As well as chef—that’s a dream job that people are like: I always wanted to do it, but I worked for a couple of years and now I’m going to culinary school. Also, a lot of the artsy careers, like jewelry designer. There are only so many jewelry design majors in the world.

Can some of these jobs be started as side jobs before a person transitions into them full time?
Yeah. Real estate broker is definitely one. You can’t really start as a chiropractor on the side, but event planning is something that people can do. They’ll work events on the weekend in whatever capacity they can—whether they’re assisting the event planner or working as a waiter to learn more and more before they make the leap. And definitely in the film world—so many people will PA [work as production assistants] while they’re still bartending.

Your book is full of day-in-the-life snapshots. So what does your typical day look like?
I wake up at 8. I complain until 8:30 about waking up at 8. My wife and I argue over who’s going to walk the dog. I win. I go to the gym (let’s say it’s a good day). I come back and answer E-mails. Then I’ll try to write from 10:30 until 12:30. I’ll work on, say, a screenplay. Then I’ll go get lunch. I’ll read all the Hollywood gossip. It’s very important to me. I need to know what’s happening with Brad and Angelina. Then in the afternoon, I’ll go back online and return E-mails. Then from 1:30 to 6:30, I will write—let’s say now I’m working on a novel—with a break in there to make a bunch of phone calls, because now L.A. is open. Then I come home, and it’s my turn to walk the dog. Then I work pretty hard from 8 o’clock to 10 o’clock. I do whatever writing strikes me while simultaneously watching something on TV. Somewhere in there is dinner.