To initiate the best possible execution of the glitch, you need to start early on in the game. During the initial building of Norune Village, make sure that Pike is placed into Paige's House prior to completing Old Gaffer's Buggy, so as to obtain the better selection of items at the shop.
Upon doing this, next you need to go to Old Gaffer's Buggy and shop. Hover the cursor over the Ice attachment and simultaneously press the X button and Right on the D-Pad. It may take a few tries, but you'll be holding a Broken Dagger in the Attachments menu (or, occasionally, something else).
This Broken Dagger can usually be used as an attachment on weapons to mess with stats. Most of its known varieties will max the weapon's stats when an odd number is placed on the weapon, as well as adding several abilities, although they are merely temporal. Regardless, you'll obtain a weapon that will Build Up after the next upgrade.
Another use is placing many of them on a weapon and selling this weapon to the Old Gaffer (it only works there). Generally, you can obtain obscenely high amounts of Gilda back from this.
Please note, however, that the glitch is best done using the above method and offers the highest known rate of success. Using it in alternate situations can cause you to receive beta/glitch items and maybe also cause game freezes. Done properly, however, you'll be guaranteed easy battles and easy Gilda!