I am in the market for a new turntable. Any suggestions on which I should get? It needs to be at least 12", have good/steady rotation, and a smooth surface (that is to say none of the cheap Wilton ones).

This is just my opinion, but the next time I'm in the market for a turntable, this will be the one that I purchase.
https://www.atecousa.net/Merchant2/merchant.mvc?Screen=PROD&Product_Code=612&Category_Code=dstands&Product_Count=1

I used ones like this in culinary school and they're wonderful.

I love my Deluxe Reversible Formica Turntable by CK Products. It is also available through Amazon. It is less expensive than some of the others, but is very sturdy and allows you to more easily work on square cakes and sheet cakes.

for the smoothest rotation, get one with ball bearings. I have the Ateco one linked above, and while it is a wonderful, solid stand, it becomes harder to keep moving when bearing weight. A ball bearing will keep you going with less slowing and starting with your hand.

I love my Fat Daddio turn table.