Modding Borderlands is fairly simple and is easy to do with a few basic tools and skills.
First and most important part of modding Borderlands or anyother game is having a way to transfer
your saved gamed to your computer. Some things that will help you with that are listed bellow:
Some Way to Transfer Data (360 only):
Microsofts Data Transfer Kit- Around $15
Datel XSATA- Around $50
Datel XPORT- Around $50
you may also use a USB stick/Flash Drive now, some programs you could use are, USB XTAF Explorer or, Modio. The USB device must be at least 1GB in size or you cant use it also, you can only use up to 16GB of space.
Game Save Editors:
WillowTree on SourceForge - 360, PS3, and PC (Recommended)
Gibbed's Save Game Editor - PC and PS3 (Good for Patch 1.21 and below)
HxD - Hex Editor
There are also a bunch of other Standalone Borderlands Save Editors going around
Basic Guide Lines for Modding:
If you choose to ignore the following guidelines it is very likely they wont appear in your backpack.
This is because as of patch 1.30 which keeps out overpowered weapons.
1.Use the same Manufactuer throughuot your weapon or item. No missmatcing.
2.Dont use parts from dlc's unless you have that dlc. No parts from Mad Moxxi's if you don't have Mad Moxxi's.
3.Use the correct parts. Dont use sights for barrels and mags for stocks.
If you wish to get more powerful weapons I suggest experimenting with stock parts.
Borderlands Weapon Editor v2 - Helps build weapons from scratch. Created by Synthpixel.
Gear Calculator - Build weapons from scratch and have a variety of weapon stats calculated for you. All Knoxx guns are now supported. Export to Willowtree also supported.
Willow Shrubbery - Online save file viewer/browser. View gear from either your own saves or other people's saves. Also interfaces directly with the Gear Calculator.
Rehasher + Resigner:
Through some personal testing with Gibbed's Save Game Editor, you do NOT necessarily have to use the correct parts on the correct weapons.
Example: I've used rocket launcher, pistol, smg, and shotgun parts on a sniper rifle.
The weapons viewed in-game physically may appear to have missing parts, but they usually function correctly.
Also: you don't even have to use magizine parts in the mag slot, or scope parts in the scope slots.
Mix and match and see what you come up with, some bizarre weapons are possible.