I'm adding this because I remember when I first joined this wiki I had some trouble with categories and no one would really tell me what categories to add. Hopefully some new users will find this useful.
Categories are important and per the rules you must add them or face a three-day ban. However, with the exception of the franchise categories mentioned at the end of this guide, do not just make up non-existent categories (that can also get you banned).
A complete list of categories is here. However, please be aware that although we the admins do our best to keep the wiki free of fake categories, it is still an ongoing process, and sometimes made-up categories slip through the cracks. Therefore, don't assume that the fact that a category is on this list and that it shows up in the drop-down que when you start adding categories means it is legitamate. When in doubt, click the page for the category in question. If there is only one pasta in that category, and the category was created by someone other than an admin, and it does not have a formal description (and it's not a franchise category), chances are it is a fake category and you should not add it (in fact you are free to delete it if it is clearly a fake category).
Here are some examples of common fake categories that new users keep adding:
"non-gaming" (the correct category is "Real Life")
"Pokepasta" (the correct category is "Pokemon")
"First Creepypasta" (we really hate this one)
"mods" and "video game glitch"
"creepypoem" (the correct category is "Poetry")
categories for consoles or game developers (e.g. "GameCube" or "Nintendo")
categories used more like tags on Youtube (e.g. making a category for the title of the pasta, the name of the narrator, settings, or insignificant objects mentioned within the pasta)
names of notable video game characters (e.g. "Ash", "Professor Oak", "Link", "Snake", "Knuckles", etc.)
"Lost Episodes" (the closest thing on this wiki is "Television")
"shock ending" or "twist" (the correct category is "Mindfuck")
and speaking of the aforementioned, any of the standard categories on the Creepypasta wiki (just because it is a category on the Creepypasta wiki doesn't make it a category on this wiki. We usually have our own versions of them)
categories for popular creepypasta meme-monsters (e.g. Funnnymouth, Smiledog, The Rake, Jeff the Killer, Mr. Widemouth, Slenderman, etc.)
correct categories that are mispelled or have incorrect case use (e.g. "Real life", "Original story"; the spelling that appears in your drop-down que is most likely the correct spelling.)
"Creepypasta " and "Creepypastas"
These two are a given. Unless you are writing a guide or something like this, always add those two categories.
"Video Games" or "Real Life "
If your pasta is a gaming pasta, add "Video Game" and "Video Games". "Real Life" is the closest thing we have to a "non-gaming" category. Do not add this category to gaming pastas and gaming mindfucks. Also do not add it to pastas that are set in fictional universes.
Note: contrary to the impression the name of the category may give you, a pasta does not have to be based on a true story in order to qualify as "Real Life".
"Original Story ", "Migrated ", or "Sequel "
If you are the original author of the pasta you are uploading, and it is not a sequel to anything, add "Original Story ". If you are importing it from the Creepypasta wiki or someplace else, add "Migrated ". Note: Please remember to ask permission from and to credit the original author before migrating a pasta if you can find him or her. If the author is anonymous than the pasta is fair game, but please say so on the page.
"Sequel" is self-explanatory. Add it if your pasta is a sequel to another, either your own or someone else's.
Do not make specific game titles into categories. Instead, use the name of the series or franchise to which the subject of your pasta belongs. For example, add "The Elder Scrolls ", not "Skyrim". If your pasta focuses on games from two or more series, add "Crossover ".
Do not add categories for consoles or development companies.
So there you go, four categories you can automatically add if your pasta is a non-gaming one and six if it is a gaming pasta.
Other Popular Categories
Awesome: Sure, go ahead and add this one, it's a free category edit
Ritual: For ritual pastas.
Journal: For pastas that are written as simulated diary or journal entries.
Holiday: For pastas that revolve around holidays, usually Christmas.
Dreams/Visions: Self explanatory, but please be aware that this wiki is not the place for you to upload pastas about whatever weird dreams you may have, unless those dreams actually make for a compelling pasta. If you just want to tell everyone the crazy dream you had last night, we have a special page for that.
Needs work : If your pasta is assigned to this category it means that it is lacking in quality or has an issue that needs fixing. You will have one month to improve the pasta or fix the issue or it will be deleted.
48 Hours to Deletion: This is for pastas that are either downright terrible or have serious or multiple rule violations (usually both). The name is self-explanatory. If you think a pasta should be added to this category due to being an obvious trollpasta, having major rule violations, or just being terribad, add the category Pending Review. Note: Please be sure to state your reason for adding the pasta to Pending Review, either in the edit log or the comment section.
SOG-Read : You do not have to be an admin to add this category, but if you do it must be to a pasta that has actually been featured on Haunted Gaming.
Creepypasta of the Month! : Self explanatory, do not add unless your pasta is actually a CPOTM winner (even if it was nominated).
Other Misc. Categories to Be Aware of
Fixed: For pastas that were in "Needs work" or "48 Hours to Deletion" but were fixed by another user.
Seecret Auron Edition: A long time ago in this wiki's history, we had a certain chat mod who sometimes "fixed" pastas marked for deletion by turning them into parody pastas. The mod hasn't been active on chat or wiki for several months and this is pretty much a dead category. I will probably go through the category some time and delete all the pastas. But this is just incase you see one of the pastas assigned to this category.
Work in Progress (WIP): Please be aware that works in progress are frowned upon on this wiki. If you write a work in progress, it will be put in "Needs work", unless it is barely started in which case it will immediatly be assigned to "48 Hours to Deletion".
Needs Categories: After reading this guide you shouldn't need to add this category, so please don't. Just add the relevant categories.
HAHA OH WOW!, DO NOT DELETE, SHH GO AWAY, Pretend There's No Categories Here, etc.: These are for trollpastas that the admins find too lulz worthy to delete even though they are technically against the rules. Please do not upload a trollpasta hoping it will recieve such an exemption, as most trollpastas aren't that good, and yours is probably no exception (and you will still most likely be blocked even if it is). I am only putting these categories on this guide so that you know what they are for and don't add them to pastas where they don't belong. If you are not an admin, don't add these categories.
Troll Pasta and Category:Trollpasta: Once again, trollpastas are against the rules. But there are two reasons why we have these categories. One is to apply them to the trollpastas that have been placed under protection as mentioned above. The other is so that you and other users can flag trollpastas that have been uploaded (if you see a blatant trollpasta that hasn't been put under protection, please also add Pending Review).
Collaboration: A new category created for pastas that are the collaborative effort of two or more authors.
Very Moist : A vanity category created by one of our former admins. Do not add this category.
Translate: For pastas that have been translated from a language other than English and may need some fixing up.
Fanfiction: There is actually one exception to the rule against trollpastas, and that is that you are allowed to write and upload SOG fanficiton. But please only do this once in a while. Also please remember to ask permission from users before mentioning them in fanfiction.
How to Actually Add Categories
To actually add the categories, either click the green "edit" button in the toolbar and start typing them in the "Add category..." que of the catgory box near the bottom right-hand corner of your screen or just click "Add category" in the category bar below the foot of the page. Be sure to hit "enter" after each one.
Note: You are free to add relevant categories to any pastas that lack them, not just your own.