Note to other Moderators: Don't edit this to have things for future MC Versions, just make a new Thread for that and keep this for legacy.
Crafting Recipe of [insert Item here] doesn't work, why?
Most Crafting Recipes on the Wiki are outdated. I guess some Wiki people might update them later if you point that out. Use NEI or Craftguide to get the proper Recipe.
How do I get Iridium?
Loot Overworld Dungeons, and certain modded Dungeons that use Overworld Dungeon Loot.
Why doesn't my Mass Fabricator produce UU Matter?
Nowadays Mass Fabricators produce UUM in Liquid form. There is a Tank Gauge that fills up on UUM very slowly (1mB per operation is normal). Hover over it with your Mouse to see its precise amount. A Fluid Ejector Upgrade might be useful if you just use IC².
My FTB Pack doesnt generate IC² Ores, why?
FTB Packs use CoFH Ores instead of IC² Ores. Turning on a Config in IC² may fix that Issue.
Why is IndustrialCraft Steam not compatible with Railcraft or other Mods Steam?
IC² uses its own Steam Fluids, therefore it is not the regular Steam other Mods use and not compatible with it.
Where are the Recipes for Stuff?
IC² lacks NEI Plugins for certain Machines, meaning you cannot look up most of the things, especially Fluid related things.
Why doesn't my Pump work?
The Black Circly thing has to be touching the Fluid. Use Wrench to move it to the direction you want to face it.
What happened to the Energy Net?
I don't know. Player is responsible for that.
How does my Iridium Drill get Fortune/SilkTouch?
IC² Mode Key + Rightclick
How do I get Quantum Flight Mode and Jetpack Modes to work?
IC² Mode Key + Jump
Canning Machine doesnt can anything for me, why?
You need to switch the Mode of the Canning Machine for certain Tasks. Just like the Metal Former has a Mode Button. Also NEI is not functioning 100% with this Machine.
Ejector Upgrades don't work properly with Hoppers etc, how can I fix that?
Shift+Rightclick a side with the Ejector Upgrade before inserting it into any Machine. That way it will only eject into a certain direction.
Where are the Config Files for IC²?
It is the Files that end on ".ini" instead of ".cfg" or ".txt". You can open it like the others with Notepad.
Why arent my Hydration Cells working in Cropmatron?
Try Universal Fluid Cells with Water instead.
How do I protect myself against Radiation Poisoning?
Wear a full Hazmat Suit. That means Scuba Helmet, Hazmat Shirt and Pants, and Rubber Boots.
What happened to Coal Fuel?
Rationalised away. Not available anymore. Sadly.
Magnetizer doesn't work?
It now has to be NEXT to the Fence rather than below or above it. This is to make it more useful for longer distances. 
My Steam Generator won't stop "exploding" or "fizzing", how do I stop it?
place Condensers adjacent to them to fix it.
How to I make Reinforced Stone?
Place an Iron Scaffold and CFoam it in order to make Reinforced Stone. Yep, no Crafting Recipe for that one, you have to do it in world.
Why doesn't the Ejector Upgrade with BC Pipes?
That requires additional Compat work on our Side. Maybe it will be added later.