Here is another good place for intro information: Oblivion Mods FAQ (Frequently Asked Questions)
Modding for Oblivion can be done at multiple levels with multiple levels of skill and required knowledge.
- Creating savegame characters - This is the process of configuring a character at the start of Oblivion and saving your game.
- Creating plugin modifications - This requires a version of the Construction Set and a desire to change something in the game. With this, you can change the stats on weapons and armor, create new races, create new NPCs or creatures to fight, create buildings, quests, etc.
- Create texture modifications - This requires a graphics manipulation program and some required support tools such as a BSA extractor, DDS Converter and maybe even NifSkope and a Normal Map tool such as CrazyBump.
- Create new models - This requires a 3D modeling program such as Blender and some required support tools such as a NIF converter, NifSkope and a graphics manipulation program. With this, you can create new weapons, armor, creatures, architecture, etc. never before seen in Oblivion.
- Create new animations - This requires a 3D modeling program such as Blender and some required support tools such as NIFBlend and NifSkope.
- Release your mod - This can be viewed as a boring step but what you do here can have long-lasting impact on the modding community and you should consider this just as important as any other piece of the puzzle.
- Creating savegame characters - This is one of the least complicated ways to provide content for the Oblivion community but it still requires time, knowledge and preparation. When creating a savegame for distribution, it is recommended that you disable all installed mods other than what is absolutely necessary to create your character (such as a custom race mod like Slof's Clouded Leopard). Then you have the decision to provide the savegame at the initial prison cell before the tutorial starts and / or provide a savegame of the character just prior to existing the sewers which is just after the tutorial. You can also use template savegames that have done this already and use Oblivion Face Exchange Lite or Wrye Bash to copy your face to another (more standard) savegame template. (Example: Oblivion Face Totality Pack). You can use the Savegame Manager tool in Oblivion Mod Manager to see what plugins were enabled when a savegame was created. When finished, see the step below on how to release your mod.
- Creating plugin modifications - You will need to download the Construction Set from TESNexus or the Official Bethesda site. You can then get information on how to use this tool from the Construction Set Wiki. Once there, you can find helpful areas such as the Getting Started Guide, Scripting details and Tutorials. You can also download a compiled resources of online information in a file called Oblivion Mod Makers Manual. When finished, see the step below on how to release your mod.
- Create texture modifications - You have two options here: Create texture replacers that change all occurrences of the texture in the existing game which does not require a plugin or create new and custom items that use these textures...thus unique items that did not exist in the game prior to your plugin. The textures are in DDS format and will require conversion to/from your image manipulation program to/from DDS format. Here is a comprehensive list of DDS Tools. When finished, see the step below on how to release your mod.
- Create new models - There are many 3D modeling programs out there but for the new modeler on a shoe-string budget, it is hard to beat Blender and the vast amount of tutorials available. Other tools are XSI Mod Tool (free), GMAX (free), Milkshape 3D (trialware), Autodesk Maya (commercial), Autodesk 3DS Max (commercial) and Lightwave 3D (commercial). When finished, see the step below on how to release your mod.
- Create new animations - Start with animation tutorials. When finished, see the step below on how to release your mod.
- Release your mod - After you create and test your mod, you will need to create a Readme file and some screenshots. If your mod does not utilize any of the 1.2 patch scripts, you might consider back-reving your plugin to an older format so it can be used on non-patched versions of Oblivion. It might help you save time with larger mods (more than just a plugin) to use the utility called TES4Files to help prepare and package your mod. It would also be advisable to know File Compression Basics and to acquire and familiarize yourself with the tool called 7-Zip. If you would like to support people using Oblivion Mod Manager, you could create an OMOD out of your mod and then re-convert to an archive for release as an OMOD-Ready archive that can be quickly turned back into an OMOD or manually extracted like any other archive which is the best of both world without creating two separate files. Then upload your mod to a modding site as well as some File Mirror sites for redundancy (in case the modding site goes down). Then let everyone know about your mod by creating a release thread on the Official Elder Scrolls Forums. This typically has a title of "[RELz] name of mod" and a copy of your readme file as the body of the post with a link to everywhere it can be downloaded.