In Pokemon Pearl, I need a quick introduction of effort values and more about them.?

Effort values! I know! Pokemon, when they gain levels, they gain stat points, right? Well, is it true that, pretend I was battling with my leafeon. If I faint a drapion, doesn't that mean I get 2+ defence added to my stats the next time my leafeon levels up? I need more tips into EV training. I also have a salamence, so I need some tips on EV training for it. I always battle the elite four to level up, so is that a great idea? Does protien, iron, zinc, carbos, etc....and all of the vitamins have anything to do with this? And about Effort values, is it good to train a pokemon holding an exp share without battling at all? What abut the daycare? What kind of EVS will they gain? In sunyshore I herd that a lady in the seal shope wives you an effort ribbon, but how do I do that?