At this time of posting, my primary team in Diamond is Infernape, Dialga, Tyranitar, and Staraptor. The other two slots are for evolving purposes or, in battling, some strong Pokémon. So, basically, my starter, the version mascot, a super-strong Pokémon that I bonded with when I was evolving it, and my flier that's pretty good with Close Combat, Roost, Fly, and Brave Bird.
In Black, obviously, in the start of the game, I switched out a lot. The only switching I did after that was replacing Herdier with Archen (I know its ability sucks, but it's still awesome with its massive Attack and Speed!) Unfezant with Reshiram (version mascot!) and Simisage for Zoroark (gimmicky ability FTW!)