Tagging Tips?

Okay, sorry if I'm posting way too much, but I'm just wondering exactly what you should tag a fic as. (mostly in the relationship department. Should you tag all ships, or just major ones? Or what's the difference between: fic with characters x and y interacting and fic with characters x and y interacting romantically.... sorry....)

For shipping, I would mostly just tag the primary couple. And possibly the beta couple, if they're relevant enough.

Okay... I see. That makes sense.

I tag anything major that isn't a spoiler. Like, in that Death Note fic I haven't touched in months, the SPK is the Lord British of the whole plot arc, and it's not a spoiler that Linda comes into it, because Linda is just a cipher with a charcoal pen. But Mello deciding to pull strings with my bush-league SPK catspaw main character is a pretty substantial spoiler, and I'm not tagging for him.

This can be a problem with one-shots where everything that isn't a spoiler has been done before, but.