I've complained before about how I never felt like my formal education taught me about good prose but almost nothing about good stories. So when I find advice in that vein that actually clicks with me (like Orson Scott Card's M.I.C.E. model of plotting) I get pretty excited about it. The same goes for characterization. The character-building exercise that sticks in my mind most clearly is the one I remember as the least useful: "What are ten things your character would have in their pockets?" That's a question that might tell you something about your character, but rarely the sort of things that drive a character-based story--at least, not the kind of story I'm interested in writing.
I think I've gotten better about writing active characters. (In college, I wrote one story about a high school student who did nothing but observe the people around him, and at the very end of the story, punched a locker and cursed.) But I know I'm not the only writer who's still vexed by a need, pointed out by the occasional beta reader, to make a character more "likable."
Maybe it's because I grew up watching Seinfeld instead of Friends (although I still like the schmucks on Seinfeld better than the schlemiels on Friends). Anyway. Everyone "knows" that you need likable characters, and maybe Seinfeld is the exception in the perennially misapplied axiom. And getting people to like your characters sometimes seems as confounding as getting them to like yourself.
In response to a question on /r/writing, Redditor Lon-Abel-Kelly made a straightforward observation on creating likable characters that I can't recall seeing before:
Have some idea of their ideal selves. Who they would wish to be if not for circumstance and personality flaws...There was more, but that was what jumped out at me. If you can like who a character wants to be, you can like the character. If nothing else, it's easier to find people who aspire to goodness than who achieve it to an impartial observer's satisfaction. It's also easier in fiction than in real life to show someone who a character wants to become.
You should like the ideal selves, they should be great company... You should sympathize with the ways they fail and self sabotage and you should be endeared by the little ticks of progress.
The idea of a likable ideal self rings true when I check it against successfully written characters. Many, many protagonists start of wanting to be heroes, to be brave and competent, and yet spend a surprising amount of their stories being bad at these things.
Looking at a character through this lens also exposes the whole space between who they are and who they want to be as a field for conflict and achievement within the story. When they grow, it has value. When they fall short, it's a tragedy we can share with them instead of just another reason not to like them.
This is, of course, assuming that the character wants to be someone you would like. If you know a character aspires to something that a reader will detest, well that opens up new horizons for creating unsympathetic characters. (Or does it? Kylo Ren in the latest Star Wars wants nothing so much as to be like Darth Vader, and that's so misguided and sad that he ends up sympathetic again. But maybe that's so relatable because, deep down, we all want to be Darth Vader, and the tragedy is that we shouldn't.*)
At any rate, this is a perspective I'm definitely using as I flesh out the characters in my current project, which is just at that stage where personalities and events are starting to inform each other.
* And I told myself I wasn't going to use Star Wars as an example. I was going to bring up Luke Skywalker earlier but no, I told myself, you can do better.