From Diablo Wiki
To Make a Runeword
- Items used for Runewords must be gray text items, normal, exceptional, or Elite. Low Quality, Superior, and Ethereal can be used, but you can not use magical, Rare, Set, Crafted, or Unique items, even if they have the correct number of sockets.
- The item must be of the correct type.
- The item must have exactly the correct number of sockets -- no more.
- You must socket the Runes in the correct order.
- The Runes fill the sockets in numerical order automatically, i.e. in the order 1, 2, 3, .... For example, trying to place the third Rune of a Runeword into the third socket while sockets 1 and 2 are empty will result in the Rune filling socket 1, contrary to intentions. As mentioned elsewhere, it is possible to remove an item from a socket, but the item is destroyed in the process.
- The Runeword Preparation Recipes tune equipment for receiving Runewords.
- Check the Rune FAQ for further help.