The EV system is something like this:
1. Decide which stat you want boosted, and to what extent.
2. Find a pokemon whos type matches the one you want boosted, i.e. speed=zubat, attack=victreebel
3. Battle these pokemon and watch the difference in stat growth.
Example: Treecko versus Zigzagoon
Treecko used Quick Attack!
Zigzagoon fainted!
Treecko was elevated to level 7! Spd: 15
Treecko versus Crobat
Treecko used Quick Attack!
Crobat fainted!
Treecko was elevated to level 7! Spd: 18
4. The item "Macho Brace" doubles EVs given in battle at the expense of halving obtained Speed EVs. Level up Tyranitar with Macho Brace, then give boah set=PWNAGE
5. The extremely rare Pokerus (PKRS) status condition doubles obtained EVs in battle. So, say we want to boost up Spcl. Def:
Treecko@Macho Brace
Trait:Overgrow
Status PKRS
-Quick Attack
-Absorb
-Pound
-Leer
Treecko versus Victreebel
Treecko used Pound!
Victreebel used Growth!
Treecko used Quick Attack!
Treecko was elevated to level 7! Spcl.Def: 19
If it still isn't very clear, ask someone who knows more about EVs than I do, i.e. Fwank, Bleep, etc.
If you see me posting, it's because I've been asked to. Which I guess would mean I'm taking requests.