In Anthony Bourdain's book Kitchen Confidential, he gives some insider tips like don't order fish on Mondays (they're not-so-fresh) and reconsider ordering anything with hollandaise sauce (bacteria fest). He also talks about eating bread in restaurants even though he knows it has probably been recycled from another table.
This brings me what I won't eat at Korean restaurants. When you order a kalbi or any meat dish, they'll bring out the lettuce basket so you can make lettuce wraps. The lettuce is like the bread at restaurants; It was most likely recycled from another table. At the very least, I don't eat the one laying on top since the baskets always gets stacked on top of each other.
Another thing I avoid? I don't order kimchi jjigae (stew). I've heard it's a depository for leftover kimchi.
What about you? What do you avoid eating at restaurants?