Personally, I love writing ANs. It means I'm done; I've got my whole thing edited and finalized and, for better or worse, I'm ready to post. ANs can be a place to talk about what you like in your own story, without seeming like you have a huge ego; somewhere to ask for feedback because I know you're dying to, somewhere to thank people who helped you.

There really aren't a lot of "do nots," in ANs, unlike summaries, and the "dos" are far more up to the individual writer, but a few things to consider.

Shout-outs are fun to write, and even more fun for the readers. I recommend using them in chapter stories (not much of a place to in one-shots, really) if they're your thing; I also recommend putting them after the chapter, so a reader can get right to the meat and read the chapter.

Heck, I recommend putting ANs after the chapter in general, for just that reason. It places the focus on the story, which is what's important. However, notes before can be effective, too; maybe as a warning that a chapter contains more violence than usual, or if there's something urgent you need to get across to your readers.

(Edited to add: FFnet has now forbidden shout-outs, so that only applies if you're posting at a different archive, anyway.)

My only real suggestion on what to avoid is putting notes within the story itself. If you do so, you do it at your own risk; even set aside in parentheses, it breaks up the flow. No matter how cute you think your characters are being, wait and put the "awwwwww," at the end.

ANs are where the story becomes personal; where you get to put a face with your writing. It's a way to build up recognition and to let your readers get to know you. The more familiar you become to your readers, the more likely they are to keep reading, or to read something just because you wrote it.

So have fun, kick back, and enjoy the fact that you're done with your story or chapter, or what have you.