What are some rules that you keep true to while putting together your Pokemon team?
My rules are:
No Pokemon with double weaknesses.
Sure, Dragonite, Garchomp, and Tyranitar are pseudo-legendaries, but they also have major weaknesses. I once KO'd my friend's Dragonite in an equal level battle with a single Ice Beam. It didn't even get the same type attack bonus.
One legendary per team.
Making a team where you throw together all your legendaries from all your games makes your team really unfair. Plus, how are you gonna make any progress in the Battle Frontier/Subway? However, I'm fine with putting pseudo-legendaries alongside real ones, as shown by my Hydreigon alongside my Zekrom.
Porygon-Z has to be in the first slot.
What can I say? Porygon-Z is my signature Pokemon, and is always in the first slot on my team and Trainer Card. He only has one weakness, Fighting, which can be covered with Psychic. I have level 100 ones in Platinum and White.
Fire starter is in the second slot.
I always go with the Fire starter, and I really like the Fire-Fighting combo that has been present in Generations III, IV, and V.

So those are the rules I always go with when making my team. What kind of things do you guys keep in mind?

P.S. Anyone interested in a shiny Cinccino or Lunatone?