Hmm... You can't really just join the BoS or the Enclave, otherwise I'd go with "Brotherhood Scribe".
If I was just some normal schmo, well, so much depends on the setting. Obviously I'd like to imagine I could play the hero and solve the wasteland's problems but I'm not much of a fighter, or a silver-tongued manipulator. If I was in the west, I'd probably end up in some minor research role with the Followers. In the east, well the setting is so messed up there's no real point looking for realism in it. Although it would probably be something along the lines of "get shot".
There's also the fact that I'm making these assumptions from the point of view of a 21st century, university educated, western European. If I had grown up on a Brahmin ranch in 23rd century New Mexico, I would probably have a different perspective.