Its all about synergy, and knowing what the opponent is going to use. For example if something like an Infernape comes out to Blissey, you should probably go to Dusknoir to take the Close Combat, before you do this, you must think, what if Infernape uses nasty plot on the switch? There are too many things to think about during a match to teach. I will teach you, but first you must do something by yourself, I recommend using Shoddy Battle, and doing some battle there, so you understand the metagame, I can help from their. Thats the best way to learn the basics