I agree with JediMaster362. Two of my favorite ships of all time, Zutara and Jetko, are admittedly ships between enemies, and the latter breaks my rule of multiple instances of caring, since it is wildly one-sided on Jet's part at best. However, they are the exception to the rule because Zuko reformed and Jet couldn't handle it well. 95% of Foe Yay ships, like Azula/Aang, Crowstiel, Samifer, are either crack ships or based on subtext. Crack ships are usually awful to begin with, and subtextual ships are often queerbaiting and forcing fans to do all the legwork when it comes to queer representation.
For starters, no incest, no adults getting it on with minors. Now that that's out of the way, I think the characters have to have connected intimately with each other in the series. They cannot be enemies, they definitely need to have actually met, and they have to have had multiple instances of caring for each other in a way that could be interpreted as romantic.
I HATE incest ships and think they should all burn in hell!
Oh yeah, my NOTP is also Thorki. No Yay all the way for incest
I've got a couple:
Jon/Dany from Game of Thrones, Jemma from The Dark Artifices, Clabastian and Isabastian from The Mortal Instruments, and Calypso/anyone from the Riordanverse. After reading the 2nd book in The Trials of Apollo, where Apollo declares Calypso could be his babysitter, I realized: Calypso is thousands of years old. She is an adult. She has dated ADULTS. Percy was 14 when they met. Leo is 16. 99% of the main characters are teenagers. Suddenly Caleo and ESPECIALLY Percalypso become a whole lot less cute and jump into "ewwwww!" territory.