Hint: If you have to put 'If this post isn't allowed please feel free to remove it', then you should probably contact me and ask, as it says on the profile page, instead of adopting a 'post and be damned' attitude. That gets your post deleted and me pissed off.
I try not to come down on anyone too hard if they mess up somehow, especially if they seem to be a newbie just learning the ropes, but there are limits. A lot of you have been here for quite a while and know what you can and cannot get away with, but I am still the #1 moderator here, (txrabbit is co-mod in case of emergencies) and any problems need to be brought to my attention, not just posted on the comm. That way lies pointless wank and often the terrorising/traumatising of newbies.
I don't mind it if people email/PM me to check that a post is acceptable. I prefer it. I hate deleting inappropriate/unsuitable posts, but I will do it and feel sick about it later.
Now, to the subject of headers.
Titles are important, as are ratings. Newsletters can be quite picky about that kind of thing. No rating, no link. No title, no link. And how are people supposed to rec 'that fic with no name, you know the one...' :/
Warnings/squicks are important. Some people need to decide whether or not they want to/are capable of handling the content of your story. If you want to give people the option of not reading your warnings, this piece of code is very useful:
**<span style="background-color: #FFFFFF; color: #FFFFFF">stuff you're hiding</span>**
which does this:
**stuff you're hiding**
A Summary is also useful, for somewhat the same reason - to let people know if this is something they want to read. Just a line or two can be enough to capture people's interest. Or not.
A link to previous chapters is something you should always consider, whether it be a master post, a tag, a section in your memories, or even a link to another archive. If someone joins the comm, finds your chapter 17 and can't immediately access chapters 1-16, they might not bother trying to hunt them down and instead just scroll on by.
If you use a beta, name them! They deserve recognition for their work. if you're not using one, and want one, look to the Bloodclaim Betas post (also linked in the list just below the dragon counter).
You don't have to go overboard. If your headers look like they're going to end up longer than the fic/drabble you're posting, be sensible about it. Remove the ones that aren't necessary; maybe squish a couple together.
In conclusion, headers are there to help both the reader and the writer. If someone looks at your post and can't tell what the fic is about, they're likely to scroll past. That doesn't benefit them or you.
I've had someone read one of my fics in a fandom they didn't know because of the warnings/squicks I listed in my headers. One person's squick is another person's kink. ;)
Headers - useful if used correctly. Don't go mad with them, but use them wisely and we all benefit.
Carry on Spandering!
*ETA: Be sensible about the warnings/squicks, but understand that you are never going to satisfy everyone. It's just not possible, and trying will drive you mad. ;)
ETA2: Two useful links:
Headerbuilder, link provided by heuradys.
advice on fic headers by penknife, link provided by vichan.