The guild system would be some guide. Lawyers and Doctors existed in that era (and in Roman times).
Also I presume you mean in Europe. The rest of the world would have a different answer.
Holy mother of trades! Thanks! 
Well yes, but answers from the rest of the world is also welcome. I want it to be as broad as possible- have any input from the rest of Earth :)?
Midwife, Abortionist, Pimp, Soldier, Sailor, Undertaker, Torturer, Rabbi, Mohel. The first two occupations often overlaped.
That was about the same time most people were beginning to have last names. Often those names were taken from their professions. So look for professions that are also common last names.
Miller
Smith
Black[smith], Gold[smith], White[smith], etc.
Green[grocer]
Cooper (barrel maker)
Tailor (maybe spelled Taylor now)
Carpenter
Fisher
Brewster
Baker
Parson, Bishop, Deacon (now Dean)
Thatcher
Clerk (now Clark)
[Wheel]Wright
Cook
Hunter
Tanner, Skinner
There are many of them – I’d guess about a third of Last names come from old professions.