This post is intended to be a full guide as to making, installing, and uploading mods so that others can download them.

First of all:

DO YOU HAVE FILE EXTENSIONS ENABLED?
If you see filenames as stuff.stf, then yes. Otherwise, no. If you do not have file extensions enabled, then you can ignore me when I say "name it as stuff.stf", and instead name it as just "stuff". The rule is, keep the .stf on the end of the filename.

LOCATE YOUR ACE OF SPADES INSTALLATION:
It should be in C:\Ace Of Spades\. Type this into the address bar of Windows Explorer. This folder contains the files you will be editing.

THE TYPES OF MODS:

1. The KV6 mod. This is a mod that changes the shape/colours of the intel/gun/command post/nade/pick/spade.

2. The sights mod. This is a mod which changes the ironsight (what you see when you right-click).

3. The map mod. This is a custom map. I will not be documenting the map-making process here, as I am not too familiar with it.
COULD SOMEBODY WHO MAKES MAPS POST A "MAKING MAPS" SECTION. I WILL EDIT TO INCLUDE IT.

MAKING KV6 MODS:

The Tool:
SLAB6
Slab6 is the tool that lets you edit .kv6 files. These files are found in the "kv6" folder of your Ace of Spades installation directory.
MAKE A BACKUP OF THE FILE YOU WILL BE EDITING

Extract Slab6, and open the program. Press L to open a file, or user the menu: File --> Open.
Press F1 for help in Slab6. Use the Insert and Delete keys to insert and remove blocks. Use right-click on a block to grab that colour. Use Space to paint the block under the cursor. Save it.

Voila! Your very own gun/nade/tool. It isn't in the game yet, though.

MAKING IRONSIGHT MODS:

The Tool:
You will need an image editor that can support transparency and layers. Make yourself familiar with your chosen tool, especially familiar with transparency and layers.

MAKE A BACKUP OF THE FILE YOU WILL BE EDITING.

You will be editing the file called "semi.png" in the "png" folder, in your AoS installation folder. Make sure that you keep the center of your sight on the four red pixels of the original sight, otherwise your bullets will go... elsewhere.

INSTALLING MODS:

To install a mod, it needs to be the right name, and in the right place. Ironsight mods are called "semi.png" and go into the "png" folder in your Ace of Spades installation. The names of KV6 files tend to be self-explanatory, and "semi.kv6" is the gun.

REMEMBER TO MAKE BACKUPS BEFORE INSTALLING MODS

UPLOADING MODS:

To upload your mods so that others can download them, you need to find a file host. In my opinion, MediaFire is the best. It's free, and it doesn't force anyone to wait. You will need to make an account, and click "Upload files". Select your mod. Copy the link, and post it on the forums.

DO NOT POST YOUR MODS IN HERE. That should be all. I do not plan to post, only to edit this post.