How to EV Train Your Pokemon  

  
EV training is rather complicated, but the rewards of EV training a pokemon are wonderful.  With EV training it is possible to choose to increase the pace at which a particular stat receives points.

The idea is, as soon as a pokemon faints a different pokemon, it gains exp points and EV points.  The EV points are dependent upon the pokemon that gives experience.

So, say you battled and killed a wild Magikarp.  Magikarp gives 1 EV point towards your rate stat.   Share to EV train over one pokemon in time) has 1 EV rate point.  1 EV point won't do anything; however, in the event that you battled, say, 4 geodudes, the pokemon that profits experience from all of them will gain 1 stat point towards the desired state.  Each 4 EV points = 1 stat point. 

A single stat will hold a max of 255 EVs each stat.  Furthermore, a pokemon can only receive 510 EV until EVs have no effect on it anymore.  Therefore, you must plan out how you distribute EVs for your pokemon to get the wanted stat rise you need.

Battling 255 magikarps could come to be very tiring, so instead you can give it some vitamins (IRON, to be exact ) irons will give 10 EVs into the stat it states it's going to raise.  There's a catch though.  You can only give a pokemon a max of 10 vitamins each stat.  Consequently, in the event that you wished to give yer, say, Empoleon max defense, you can give it 10 irons to receive 100 defense EVs, but the other 155 EVs need to come from fighting other pokemon.  You might also fight stronger pokemon, for example, a machop gives 1 EV point towards attack and a choke gives you two EV points towards attack.  So instead of fighting 255 matchup,s you can fight 128 Machokes

EV training, together with selecting a good nature to your pokemon, can make give your pokemon a huge stat increase.  Like this, you can turn out to be almost an unbeatable coach.

Note
The stat bonuses won't show right away if they're at a low level.  They will show up as the Pokemon has to level 100.  By the time it's at par 100 it would have all the stat bonuses that you made it earn.