INCOMING WALL OF TEXT FOR REDFEATHERRAVEN
Team Building 101
Metagame
The metagame of the 5th Generation revolved around controlling a weather condition (rain, sandstorm, sun). However, the abilities Drought, Sand Stream, and Drizzle have all been nerfed, so going into 6th Gen, there isn't a set precedent. However, the abilities of entry hazards (Spikes, Toxic Spikes, Stealth Rock) have not been nerfed (to my knowledge), so you will be seeing those often.
Stealth Rock
Almost all competitive teams involve a Stealth Rock user. If you're unfamiliar with the move, it deals 12.5% (1/8) of a Pokemon's HP whenever it switches in.
However, being a Rock type move, it applies weaknesses and resistances. The sole existence of this move has limited the ability of 'mon such as Charizard, Moltres, and Yanmega.
Rapid Spin
This move is one of the sole outs to Stealth Rocks. It instantly clears the field of all entry hazards your opponent has set up, but keeps your own. However, some teams, such as those with many Rock and Steel types, may not need to use a Rapid Spinner.
General Tips
- A team should have no more than three Pokemon with a weakness to the same type (this is a limit. Two and lower are optimal).
A team should have outs to the most popular 'mon in the metagame (irrelevant for now)
A team should have Pokemon that fill different roles (exceptions covered later on). For example, a team of six physical sweepers may automatically lose against a single Skarmory or Avalugg.
Roles
Pokemon tend to fall into three types of roles, and those roles are further divided. Each role features Physical (Attack/Defence specialisation), Special (Sp.Atk/Sp.Def specialisation) and Mixed (strong in both fields).
Sweepers: The primary attacking forces of a team. Sweepers are meant to come in, (optionally) boost their stats with a move, and then lay waste to the opponent's team with powerful attacks that hit a variety of Pokemon for Super-Effective damage.
A good example of a physical sweeper is Blaziken. After it comes in, it can use Swords Dance, followed by protect. You now sit at +2 attack and +2 speed (from Speed Boost). Flare Blitz and High Jump Kick will OHKO most anything that tries to stop it, especially after a Mega Evolution. Of course, note the recoil risks.
A good example of a special sweeper is Latios. With a life orb attached, Draco Meteor will OHKO anything that doesn't resist it. It boasts the speed and power to revenge kill effectively. In addition to hit-and-run tactics with Draco Meteor, it has access to other powerful moves, such as Surf and Psychic.
A good example of a mixed sweeper is Infernape. It has access to both Nasty Plot and Swords Dance, but also has a base 104 stat in both without a boost. This makes it unpredictable to the opponent, and moves such as Flamethrower (special) and Close Combat (physical) have the ability to counter the titans of physical and special defence, such as Skarmory and Blissey.
Tank: A major problem with sweepers is frailty. A single priority move or good hit will take it out. This is where tanks shine. Usually, tanks exchange the blazing speed of sweepers for high defence or special defence, allowing them to take hits.
As it was mentioned earlier in the thread, we'll use Avalugg as our example of a tank. An already high attack and defence can be boosted by Curse. After a few boosts, anything outside of a critical hit is not going to be KOing it from the physical side.
The attack stats aren't always matched by the defence stat, however. Slowbro is a notable example, featuring high defence and passable Special Attack. It also has access to the move Calm Mind, which patches up any holes in special defence and raises Special Attack to a more threatening level. The hidden ability, Regenerator, allows it to leave battle and come back in with restored health, making it an MVP in long battles.
Mixed tanks are those with high defence and special defence. Swampert is a great example. It has passable defencive stats and a 110 attack stat. With only one weakness, to a type that has been rarely employed in past metagames, Swampert has the ability to annoy the opponent and deal damage. It has the ability to run support moves, such as Stealth Rocks, but can also set up with moves like Curse.
Just because it is one of my favourites, I'll mention Porygon2 as another mixed wall. With an eviolite and 252/252 investment in the defenses (neutral nature), the stats reach 418 and 433, respectively. It also has a base 105 Special Attack to work with to fire off Ice Beams, Discharges, and Thunderbolts; the ability to heal with Recover; and the power to spread status with Toxic or Thunder Wave.
Wall: Pokemon that focus on support more than dealing damage. Examples of support moves are rapid spin*, stealth rocks, light screen, reflect, thunder wave, and toxic. They focus on grinding down the opponent and helping out the other members of the team.
An example of a physical wall would be Skarmory. It has the ability to lay down Spikes/Stealth Rocks (Stealth Rocks is not available for Skarmory until Pokebank, however), can force switches with Whirlwind, can recover with Roost, and can deal damage with Drill Peck or Brave Bird.
The most iconic special wall is Chansey, a gen 1 staple and star user of the Eviolite. Even Focus Blast, a fighting type move with 120 base power, has trouble getting a OHKO on Chansey, bar a few of the most powerful users. Chansey can use Wish to heal any teammate completely for free, spread status with Thunder Wave or Toxic, heal with Softboiled (or Wish), and deal steady damage with Seismic Toss.
Cresselia is the first example that comes to mind as a mixed wall. Cresselia boasts a base 120HP, 120Def, and 130Sp.Def. When combined with recovery in Moonlight and the ability to support the team with Reflect and Light Screen, Cresselia can be very difficult to take out. A base 75 Special Attack isn't great, but STAB psychics can still leave a dent on weaker Pokemon.
*rapid spin is also seen on Sweepers, such as Starmie. Some people take advantage of the switches that occur when a sweeper is brought in to clear their field.
Some teams focus on overlapping roles as much as possible in order to achieve victory. I'll discuss the two main versions of those teams now.
Overlapping Roles: Hyper-Offense
This type of team focuses on straight sweepers. The goal of this team is to establish momentum and overwhelm the opponent's defences. This team is generally filled with fairly fragile Pokemon, so disturbing the momentum is a quick way to wipe out one or more of their team. Prediction is important when playing hyper-offense, but moves such as U-Turn and Volt Switch are utilised to allow one to switch out without wasting a turn of potential damage. Setu-up sweepers are also important. Using moves such as Swords Dance or Nasty Plot allows for one to power off attacks that can break through the walls they encounter. The offensive Pokemon used tend to share similar counters, with the mindset that if one of them takes out that wall, they'll have a clean path to victory. They also tend to have one Pokemon on the team that sets up Stealth Rock to wear the opponent's team, set up Reflect/Light Screen to provide defence during their sweep, and/or something with a move such as Momento that allows for a "free" switch in once the job is done.
A hyper-offense team may look something like this:
Azelf
Infernape
Alakzam
Volcarona
Lucario
Latios
Overlapping Roles: Stall
Although your comment sounds like you'd stay away from running this team, you should know how they work.
These teams focus on running multiple defensive walls and special walls, with potentially one "clean-up" sweeper. They focus on laying down hazards and using phazing moves (e.g. roar, whirlwind) and walls to force switches. One member of the team may also employ Perish Song to finish the game with certainty.
An example of a stall team may look something like this:
Tyranitar
Skarmory
Blissey
Cradily
Tentacruel
Ferrothorn
Finishing Thoughts
Based on what we can find in Pokemon X/Y currently, here are basic suggestions for Pokemon to use. Try to find ones that fit your style.
Physical Sweeper: Lucario, Blaziken, Scizor
Physical Tank: Aegislash, Avalugg, Mega Mawile
Physical Wall: Skarmory
Special Sweeper: Alakazam, Mega Gengar, Starmie
Special Tank: Goodra
Special Wall: Blissey
Other notable Pokemon of various roles include Gliscor, Greninja, anything with a Mega Evolution (although some are much better than others), and most Legendary Pokemon.
Example Team: Tyranitar, Garchomp, Aegislash, Starmie, Scizor, Gengar
The biggest weakness right of the bat is a triple weakness to Ground (if Mega-Gengar is used), but otherwise demonstrates a basic team that can deal with a variety of conditions. It has strong attack power all around and some bulky 'mon in Aegislash and Tyranitar. Both Physical and Special moves are represented. Tyranitar can use Stealth Rock, learning it as an egg move by breeding with the Tyrantrum family.
This guide is mostly just how to design the team. I probably left things out, but feel this should be enough to start. Learning how to make predictions and otherwise "play" the game is enough to be a separate wall of text. I believe Smogon is the best site for learning about things, but I'm sure Serebii and Marriland are decent. If you use Pokemon Online, each server tends to have their own forum, which is bound to have some kind of information. If anything is inaccurate in this, due to changes in 6th gen mechanics or otherwise, I figure other people will point it out.