2. I know that people date other people who are vastly unsuitable for them. I do know that. Really. And I have not been immune from screeching, "Why is he with her? Why?" or, "What in God's name does she see in that loser?" But usually when I calm down and it's been more than twenty minutes since I had to deal with my awesome friend's ill-starred sweetheart, I can think it through a bit. The bottom-feeder in question has some redeeming qualities, or has faked some long enough to fool my astute and interesting friend. If the main character (usually heroine) has a significant other with absolutely no visible redeeming qualities, I become extremely suspicious of how manipulative the rest of the book is going to be. And whether I'm going to want to spend it kicking the protag repeatedly.
3. Similarly, if the main character is supposedly awesome but has reached his/her middle age without any of the Philistines anywhere around him/her noticing it on any axis...yah. Possibly not so much with the awesome. And while I have some limited sympathy for poor little friendless waifs of 16, who have not had full control over where they were or what they were doing, poor little friendless waifs of 46 are significantly more suspicious to me. One friend. Just one. Or a mentor. Or somebody. Anybody, really. If you are truly that awesome, I really think that by the time you reach the age of majority, at least one person will be willing to speak civilly to you.
4. People in French novels speak French. People in French novels translated into English speak English, but are understood to be speaking French when they appear to be speaking English on the page. Okay so far. Yes. And there are words that just don't translate; fine. But there are words that are perfectly translatable into English, words like "oui" and "un petit peu" that in no way could be called inscrutably French. And! If you are writing a book filled with French people speaking French in France! Having them speak random bits of only high school French is really obnoxious! And you should stop doing it! Right now now now aughhhhh!
The High School Guide To Foreign Speech method of writing annoys me enough when the characters are meant to be speaking English and somehow can remember "labyrinth" and "conjunction" but not "thanks" or "apple." (I am looking at you, Gregory Benford!) But I read Le Ton Beau de Marot at a formative age, so when they're supposed to be speaking another language for the whole conversation and then have simple words of that language tossed in, my head explodes. And not in a good way.
5. The Norse gods are not varm fuzzy nice-nice. If you think they are, you are dumb. And not paying much attention.
6. I like competent protagonists. I don't mind supercompetent protagonists if they do interesting things with it. But I refuse to pant adoringly up at supercompetent protagonists just because the author wishes she had a really awesome weapon stuck in her garter. Stores sell garters. There are carry classes (where they will probably teach you that a garter high underneath a long skirt is perhaps not the best place for your only weapon, but never mind that). Go take such a class, get your cool weapon of whatever type, get it out of your system, and then go home and write characters with more than one dimension. Sheesh. Swashbuckling: yes. Mary Sue on a chandelier: no.
7. Terminal failure to care. This keeps showing up in these lists.
8. Small children, like Norse gods, are not varm fuzzy nice-nice. If you think they are, you are dumb. And not paying much attention.
9. Whimsy is like enthusiasm: if you have to fake it, it's not likely to come out right. Light touch. Light, light touch.
10. I have known several 12-year-olds in my time. Very few of them are consistently trying to sound like younger children. Most of them are trying to sound like older teenagers or adults. Keep this in mind when you're writing a 12-year-old protagonist, lest I set my 12-year-old friends on you.