The simple answer I usually give is this: you should pursue your vocation.
In answering that way, I hope to encourage students not to accept others' stories about how their lives should go, and to begin to give them some tools for answering their own question.
My reason for caution is that the word "vocation" is a tricky one. It has tendrils that grow in many directions, and some of them don't need much fertilizer before they reach into some messy metaphysical and ethical questions.
There's an important lesson in all those stories about magic that have been handed down through the ages: words have real power to change the world and to swerve the direction of others' actions. Which means they should be handled with care. "Vocation" is one of the strong words. It's got a kind of magic to it because it has the power to enchant our lives by drawing a lot of ideas together into one place, and by drawing some long arrows leading towards and away from the place where you stand right now. Its root, the Latin word vocatio, means "calling." This is what I mean by the "tendrils" and the messy metaphysics they can grow into: if you're called, that might imply a caller, which might imply some strong obligations.
Here are some suggestions for how to handle the idea of vocation with care:
First, don't tell other people what their vocation must be. Imposing strong narratives on others' lives is what we do when we pretend to be God. I don't recommend trying to play that role. Read some Milton before you do, anyway.
Second, no matter how strong your sense of your own calling, remember that we see as in a glass, darkly. You can't judge a voice except with your own ears, so remember the limitations of your hearing.
Third, and along those same lines, don't make rash decisions about the last step of your journey; look instead to the next step. This means having some humility, and a lot of patience with yourself and with your own life. It means not knowing how the story of your life will unfold, but reading it - and writing it - one page at a time.
With those caveats in mind, here are three questions that I offer students who are trying to figure out what their calling may be. I recommend taking the time to consider them thoughtfully. Write your answers down, and after a while, ask trustworthy friends who know you and love you if they agree with your answers. As you consider these questions, don't think about jobs and careers, lest that limit your answers. The aim in asking each of these questions is this: to know yourself better.
First, what are you good at? What are your skills and your strengths? Don't just think about the things you enjoy doing here; include all your gifts and talents.
Second, what do you love to do? Don't just think about what you're good at, but include those things you love but haven't any talent for.
Third, what do you want to accomplish? How would you like the world to be changed when you are done with it? How would you like to be known? What do you most want to do, or be? What would you write in your autobiography?
Do any patterns appear? As you answer these questions honestly, do you discover anything about yourself that you didn't see clearly before? Answering these questions won't sort everything out for you, and I know I can't tell you what your calling is. But I do think that getting to know yourself, your loves, your talents, and your aspirations can help you to avoid simply doing what others want you to do. And they just might shed some light on the path ahead.