Well not actually, each Pokemon gives a certain EV stat. I'm sure you know this. There are also items that can help you such as, Macho Brace (It doubles any EV's you receive from the Pokemon you defeated) And also the Power Items:
Power Weight: HP
Power Bracer: Attack
Power Belt: Defense
Power Lens: Sp. Atk
Power Band: Sp. Def
Power Anklet: Speed
Each adds 4Ev's to a different stat. It's to help you EV train faster and trust me it'll take a quite abit of time.
At most you can train two stats. It's up to you to decide which one you want. Each stat can only reach a maximum of 255 EV points.
Also you might find this helpful:
These are locations of Pokemon of give certain EV's.
Hit Point EVs - Celadon City
*Requires Surf
-Grimer (1 HP)
Starting from the Pokemon Center, go down past the Game Corner, and West until you see 2 pools of water in front of the house with the old man standing outside. Surf in the water and you'll see tons of Grimer and the very rare Muk.
Attack EVs - Cerulean City
*requires Surf
-Goldeen (1 Atk)
-Seaking (2 Atk)
Go north and cross the Nugget Bridge, then Surf along the water toward Cerulean Cave. You'll see nothing but Goldeens and Seakings so go nuts.
Defense EVs - Blackthorn City
-Geodude (1 Def)
-Graveler (2 Def)
From the Pokemon Center, just go south to Route 45, run in the grass, and beat up alot of Gravelers and Geodudes.
Special Attack EVs - Vermillion City
*Requires Surf
-Psyduck (1 Sp.Atk)
-Golduck (2 Sp.Atk)
Just go north to Route 6 (between Vermillion and Cerulean) and Surf in the little body of water to your left. 90% of the time, you'll see Psyduck. Train until your heart is content.
Special Defense EVs - Cianwood City
*Requires Surf
-Tentacool (1 Sp.Def)
-Tentacruel (2 Sp.Def)
From the Pokemon Center, just go east and jump right in the ocean where our little jellyfish friends enjoy gathering.
Speed EVs - Violet City
-Zubat (1 Spd)
There are tons of place where you can train in Speed, but the easiest by far is near Violet City in the Dark Cave. Go east from Violet City, walk inside.