I play Pokemon Diamond, and wrote down some EV training stuff on paper and it works well for me. Also, if you have a Pokemon with Pokerus, which is diagnosed when you take them to the Pokemon center. Don't worry, it's a "good" virus that boosts your Pokemon's stats.
Keep it in your party so that the Pokerus can spread to the other Pokemon. Anyway, here's my EV training list:
HP gain: Earn 2 EV points from Gastrodon, Shellos or Wobuffet.
Attack gain: Earn 2 EV points from Bibarel and Machoke (in caves).
Defense gain: Earn 2 EV points from Graveler, Steelix, Castcoon or Silicoon.
Sp. Atk gain: Earn 2 EV points from Haunter, 3 EV points from Gengar at the Old Chateau with Leafgreen in GBA slot.
Sp Def gain: Earn 2 EV points from Mr.Mime and Clefa (found in Mt.Coronet).
Speed gain: Earn 2 EV points from Staravia, Goldbat or Floatzel.
Also, it's best to have some Rare Candy with you to test if there are any stats changes/boost in the next level-up. Save your progress BEFORE you give your Pokemon a Rare Candy. If there are no changes in the level-up (like for example, the attack stat goes up by 1 and not 2 or 3) press and hold L+R+Start+Select to reset the game and try again. You will have to battle 4 (or more) of the same wild pokemon listed above so that you can earn 2 EV points. Sometime, you'll only get 1 EV point from wild Pokemon not listed here. If my method doesn't help, then try here:
http://www.gamefaqs.com/portable/ds/file/925601/48969Hopefully, this will answer all of your questions. Good Luck!