some things to consider w/vocation... which finds its roots in "vocare" literally, to call - vocation as a calling.
- sign cusping MC, placement of sign ruler (e.g. if it's Capricorn, look at where Saturn is and who he's aspecting)
- planets conj MC and their placement/aspects
- planets in 10th and their placement/aspects
Then consider these in the context of:
- 2nd house (how you generate your funds)
- 6th house (coworkers, work environment)
- overall personality (what careers suit this chart overall?)
Ultimately, vocation is a very holistic thing and I don't think you can look to one house/angle or follow a set of steps. So I don't think I can effectively answer what Saturn in 10th would indicate in terms of a profession..... It is not a question that lends itself to quick answers.
A more in depth article (A Question of Vocation) here:
http://www.astrosynthesis.com.au/articles/articles.html