NuggetBridge has come up with a simple guide that teaches players how to Pseudo RNG Abuse Eggs in Pokémon X & Y.
The method has a detailed list of pre-requisites and it is recommended that players procure all of them before starting the process.
1) A pair of Test Parents that both have different IVs. They can be from any egg group. Players can verify this by visiting the Battle Institute (Lumiose City, Northern Boulevard) since their level will be set to 50, thereby allowing for accurate results.
2) A Destiny Knot, which can be picked up from the 2nd floor, Cyllage City Hotel and an Everstone which is available from a scientist in the leftmost house at Geosenge Town.
3) i) A Pokémon with either of the following abilities: Flame Body or Magma Armor.
ii) A Pokémon with HM02 Fly
Tip: Fletchinder and Talonflame are excellent options since they both and Fly and have Flame Body.
4) A set of Pokémon that you intend to RNG. They must have at least 2/3 perfect IVs. It is important to ensure that the female (or male if breeding with ditto) has the desired ability. It is worth noting that there's a 60% chance that the offspring will inherit mother's ability.
5) A proper IV calculator.
6) Hatching O-Power. However, this is only optional.
A detailed step-by-step guide for the process can be found here, along with a relevant example of the method being performed. It is highly recommended that players check it out.
Players are required to give one of the Pokemons the Destiny Knot before dropping them off in the Day Care Centre. After hatching the egg, they're required to check the hatched Pokemon's summary and calculate its IVs.
Those satisfied with the inheritance spread, must reset the game and swap the Test Parents with another Pokemon couple that has perfect IVs matching your inheritance spread.
After this, they must hatch the egg to successfully RNG a Pokémon in X and Y.