As you may or may not know, EV's are a very important part of training any pokemon. Just starting to be recognized by people other than breeders, EV training helps pokemon become more adept in a certain area. They can be used to give any pokemon the edge in a battle, or keep a pokemon in one. For example, if you wanted to give a Raikou a boost in its Speed, you would simply train it against pokemon that's speed stat is dominant. Another example is if someone wanted to help Tyranitar land a bigger hit with Crunch, which would have that person battle against pokemon that are more dominant in Special Attack.
With that in mind, let's start with the basics. If you're wondering what "EV" means, it simply means "Effort Value." It makes sense since you need to put your effort into battling certain pokemon in order to get rewarded for your efforts. Effort Values are hidden values, so you can't just look somewhere in the pokemon's statistics to figure out how many Effort Values you have already earned for a certain stat. Because of this limit, calculating Effort Values requires you to record each pokemon, or at least the EVs gained from the pokemon. If you want an easy way to do this, just make a chart with six columns, label them according to the six different stats, and place a tally for each point gained in the stat.
So now you're in a battle. Keep in mind that only battles where EXP counts gives you an Effort Point, so no battling over a link cable or battle tower to get Effort Points. Anyway, you have a Linoone, and you just defeated a Zubat. Now, just like a pokemon's Base Values are set in stone (like Slaking always having a base value of 160 in Attack), EVs are the same way. Anyone who's ever trained a Zubat knows that the dominant stat is Speed, so if you look at the Speed EV chart, you will see that Zubat gives 1 EV to Speed. Most of the time, it's this easy. But sometimes you will find that a pokemon gives EVs in an odd stat, like Charizard giving 3 EVs to Special Attack or that a pokemon gives EVs to more than one stat, like Venusaur giving 2 EVs to Special attack and 1 EV to Special Defense. Just watch out for those things. If you can't find the EV, just use the pokedex to find it.
Now to explain how these work. Say the Linoone battled 4 Zubats and aquired 4 EVs in the pokemon's Speed EV. When it levels up, it will gain one more point to its Speed stat than if it had battled three Zubats and one Geodude (1 EV to Defense). This is because for every 4 Effort Points you get towards a certain stat, you get one point more to the stat. If you wish for a less technical explanation, let's call each Effort Value a Piece of Heart, like in any Legend of Zelda game. If you get four Pieces of Heart, you get a Heart Container. It's the same way with Effort Values. Of course, there has to be a limit to this, seeing as if you battled 3,996 Zubats, you would have a lot of time on your hands, and a Linoone with 999 located in its Speed stat.
So, what are the limits? Well for starters, you can only gain 510 Effort Values before they will stop being counted. 510 can be called our "Overall Maximum", if you want a technical term. So this brings the Effort Points you can gain to 64, once again as a maximum. But this is still a bit much to add to any one stat, and it would make any Mewtwo have an absurd amount of Special Attack still, or Blissey still having that huge potential to go over 700 Hit Points (not like you still can't get there.) So, to make it limited still, there can only be a maximum of 255 Effort Points per stat, giving a pokemon a potential 32 point increase in any stat.
So now, in terms of pokemon you have to battle, let's say you want that Linoone to get its maximum speed. You would have to battle 255 Zubats to get to the maximum speed value; EV training for any more Speed will become useless if you choose to continue after 255. Now, I can imagine some of you thinking, "Wow, I don't want to battle 255 pokemon to fill up on Speed EVs." Well the good news is that you don't. The maximum points you can get for any selected stat is 255, right? That's exactly what it is, a maximum. There are a bunch of ways to lessen the EV training and make it less daunting.
Let's start with the simplest. Remember all those Proteins at the Energy Guru that cost 9800 pokèdollars a piece? Those give 10 Effort Points to any pokemon's attack stat. HP UP, Calcium, Iron, Carbos, and Zinc are similar of course, giving 10 Effort Points to their corresponding stat. But once again, this would make it too easy to EV train and will result in a limit. The reason that those extra proteins that couldn't be used on your ultra-tough Blaziken wouldn't work could be one of two reasons: 1. The stat is already maxed out on EV points, or 2. You already used ten proteins on the Blaziken. Since you can only use 10 vitamins on a single stat, this gives you 100 Effort Values possible to each stat this way. If you're one who is looking for