Ripping Games

Ripping disc with computer
If you're lucky enough to have a supported optical drive, you may be able to rip game ISOs with Rawdump. See the forum thread for the list of known drives and instructions.

Ripping disc from Wii or Wii U
You'll more likely need to rip the disc using homebrew software on a Wii or Wii U in Wii mode. See Homebrew Channel for instructions on how to use it.

CleanRip
Cleanrip can rip a game disc to SD or USB. Note that Cleanrip will often split the ripped disc file into several pieces to fit the SD or USB card's file system. You need to put together the pieces of the ripped ISO yourself, or else Dolphin will not run it (or will just boot to a black screen).

USB Loader GX method (Wii only)
This assumes you have the latest USB Loader GX version installed on your Wii with certain cIOSes installed that is capable of playing Wii games and maybe even GameCube games from your SD/USB storage device(s). You can rip your game disc by just launching USB Loader GX and then insert a game disc, it will ask you two options: Install or Mount DVD drive - You'll want to choose "Install". It will begin ripping process to your storage device as...
 * For Wii: X:\wbfs\GAMEID_*\GAMEID.wbfs (and GAMEID.wbf1 as continuation file, if source is over 4,194,272 KiB)
 * Dolphin build version and later can accept Wii games in WBFS format.
 * For GameCube: X:\games\* [GAMEID]\game.iso (NOTE: file system must be FAT32)