I had some people wondering how they should set up their EVs, IVs and moves for their team, so here's a little guideline for a versatile, casual team that can easily work well in most situations.
Two Tanks (DoT users work fine too)
You want your scout to be any fast pokémon that can learn U-Turn. At the beginning of any fight during which you don't know what pokémon is going to be sent, have your scout up, so you can then U-Turn and have someone else sent it. Invest your EVs in speed, then the rest is up to you. You can have some attack if you want quick strikes, or have HP if you want your scout to also lay down things like hazards.
Then, your two Tanks, or walls. You need two because you need one to be centered in Defense and another in Sdef respectively. You can also have two versatile tanks with different types to have more counters (Dusclops/Dusknoir is a good example of a versatile tank). Make sure they have moves that inflict damage over time, or make them stall (for instance, by spamming curse if your tank isn't a ghost and then attacking)
Next, your two sweepers. The principle is similar to your tank, a special and a physical, or two versatile with different types (altough you'll find having versatile sweepers difficult because you will need to split your movesets). Invest in attack or Satk and speed.
Finally, your supporter. This is an interesting one because you need to think it a lot, and how good it will be will be situational and will depend heavily on what kind of team you have. Your supporter needs to be reliable in defense (it must be able to keep itself alive so make sure it is tank-ish, or "bulky"), and make sure it has support moves. Light Screen, Safeguard, Heal Bell, Weather (to help your team), Rapid Spin, Status Ailments or even DoTs (Damage over Time), it's all up to you. Personally, I like to use a DW Espeon because I go with fire-type sweepers which aren't rely durable, so I can have Magic Bounce, Physical AND Special walls and Sunny day, so for my team, it's pretty helpful (and the fourth move is up to me to decide. I could have a healing move or offense move). So, once again, you'll have to think a lot about this guy because he can be crucial and must be adapted to your playstyle for it to work well.
Hope that helped!