Various guides have been created on different aspects of XY. They provide information on everything from breeding to speed running. Links to these can be found below.
Various developments have occurred that make breeding easier than ever in X&Y. The guide 'Breeding Perfect Pokémon in XY,' written by forum member TheMantyke, covers how to breed the best possible Pokémon in XY. The second link describes the new function of Destiny Knot—guaranteeing 5 IVs are passed down from each parent holding the item.
Story Mode Guides
The first link directs to an in-game tier list that attempts to rate the effectiveness of each available Pokémon throughout an in-game playthrough. Many factors are taken into account for the ranking of a Pokémon, including its effectivness versus Gyms, move access, time you are first able to capture it, and overall performance. The second link opens up a guide that tells you the main attractions and areas you want to hit for an efficient playthrough while still getting the enjoyment you want out of the game.
These are links to miscellaneous resources dotted throughout the forums that don't really fit into any overarching topic. The first opens a thread on consecutive fishing, which is a new technique of fishing that increases the chance of a finding a shiny Pokémon in the water. The second opens a guide to EV training with hordes, a new type of battle available in XY in which the player fights five Pokémon at once with just one of his or her own. These Pokémon are generally lower in level, but can provide a massive amount of experience due to the sheer mass of Pokémon being defeated. Moving on, the third link is to a thread about the Poké Radar (back from DPP), which, via a technique called chaining, can virtually guarantee eventually finding a shiny Pokémon. The final link is to a thread describing Wonder Trades, which are trades in which you send off a random Pokémon for a random Pokémon in return.