Item Discovery works by comparing the player's value of Item Discovery against the enemies chance to drop items. As an example, if a player has an Item Discovery of 100, and a Pale Tongue has a 1% drop rate, the players drop rate will be equal to 1%. If the Item Discovery is increased to 400 then the drop rate will increase to 4%
Therefore, maximizing Item Discovery is suggested during farming otherwise drop rates will drop quite far in between one another making a farming session exhausting.
A recommended farming strategy takes place at the end of a play through (before heading into a NG+). The player can respec his or her character to reflect 100 Luck followed by equipping the Crystal Sage's Rapier (note the dex/str requirement), while wearing the Symbol of Avarice (Dark Souls III) and the Covetous Gold Serpent Ring (Dark Souls III). Following this guideline should bring a player to 350+ Item Discovery. Additionally, a player can consume a Rusted Coin (Dark Souls III) to increase Item Discovery by 50 or a Rusted Gold Coin to increase Item Discovery by 100. The Shrine Handmaid will sell the Rusted Coins for 50 souls.