EV stands for Effort Value, and it’s a process that every Pokemon goes through when it battles, breeds or gets leveled up. Unlike experience, EVs are not shared between the Pokemon in a battle and are instead allocated to its stats based on how well it performed during that particular fight. This is why EV training is such an important aspect of competitive battling.
The first thing you need to do when EV training a Pokemon is to figure out what its stats are and how much each of them should be increased. There are many different ways to do this, but the most important thing is to make sure you’re putting the EV guide into the right stats. For example, if a Pokemon is primarily defensive and can’t take down high LV lv opponents easily, then you should focus on HP and Defenses. On the other hand, if your Pokemon is a pure special attacker and can use hypnosis to take down lower LV lv opponents then put all of its EVs into Speed and Special Attack.
After you’ve determined what EVs each of your Pokemon should be getting, the next step is to find a good place to EV train it in. There are a lot of different places to do this, but the best places are generally areas where you can repeatedly fight Pokemon that give you only the EVs you need in each stat. Fortunately, there are a few spots in the game that have this type of environment, which will help you get your EVs in very quickly.
One of the best spots for EV training is right below Mt. Silver. There are Goldeens there that will give you a ton of attack EVs and, occasionally, Seaking will also be there giving you even more Attack EVs. This is a great place for fast EV training of any Pokemon that can handle it.
Another good option for EV training is the PokeCenters in Pastoria City and Canaclace City. These are the easiest locations to EV train Pokemon because they have a lot of Tentacool that will constantly drop EVs on your Pokemon, and they’re close by PokeCenters where you can heal up if needed. Alternatively, you can also travel to Valley Windworks, Fuego Ironworks or Iron Island to find similar environments.