When playing normally, players don't need much consideration what Pokemon they'll need to include to their team. Their favorite team can comprise of their favorite Pokemon with different types and movesets. You can beat your rivals, other trainers, the Elite Four and the Champions using higher-leveled Pokemon and simply exploiting enemy Pokemon weaknesses. It also helps that walkthroughs like this will give the player vital information beforehand like the trainer's Pokemon lineup, their level and other important notes to watch out for. The game also tells you what Pokemon your opponent will use.
Take note that the teams presented in this article are only a few of the many combinations. There's no such thing as a "perfect" team. For competitive battles, your luck also has a considerable part to play with. Feel free to use your own tried and tested team. This is meant to provide ideas to the players that are just starting or simply want to experiment with what Gen 6's new Pokemon has to offer. This page will feature suggestions to be used in Double and Triple Battles. Single and Rotation Battles won't be extensively covered since only one pair of Pokemon will face each other at a time.
As each team needs extensive details - down to each member's moves, EVs, IVs and held items, I'll put some references on some tried-and-tested teams especially in the highly competitive community of Smogon University.
More Sample Teams:
Have a team ready? You can have your team rated here. This will allow you to receive constructive feedback and even more useful suggestions.