...and you come to Michael, the Gatekeeper, Thanatos, the Reaper, the Great Command Line in the Sky, whatever. You're thinking, "Great, now I get to go to Heaven, or at least see what the afterlife is really like."
But the angel/god/construct/anthropomorphic personification says to you, "Hold on, not so fast. You don't qualify for the afterlife yet. The whole life you just went through is just one of multiple lives you will live, multiple worlds you will inhabit, before your soul ends up in its final destination."
He goes on to say that he's about to plop you down into your next life, which may be radically different from your one on Earth. No, he won't say how many lives you'll have, or what their nature will be. He'll only say that they tend to last about the same amount of time (i.e., up to ~100 years, more likely ~75, assuming you don't get yourself killed).
Oh yeah, and there's one more thing: You get to choose your class.
This is something of a philosophical question. The "best" choice can't be known because you don't know the specifics of the world you're going into. All you can determine is what's most likely the best choice for you--based on what you've learned in this world.
