What are the key card combos to look out for in Agricola draft?
It would depend on how you are drafting. If it's a passing draft you need to look for which cards are more powerful and probably build a synergy with those. But also notice which weaker cards are likely to come back around.

I can't really go into specifics as there are so many combinations you named a few there.


A baking strategy needs some card power to pull off well 
Anything encouraging you to early renovation would go well with any of the
stone house occupations 
Room builders can get ridiculous 
Occupations that encourage more occupations
Several Day Labour/Travelling Players bonuses


Combinations that probably don't work are Axe and Clay room builders as they are working cross purposes.

Another thing to consider in passing drafts is you can draft for wood cards even if you pass them as they are likely to be played, Church Warden, a bad example would encourage you to draft for plenty of family growth, even late family growth as long as you could ensure five peeps by round 14.