[BC]Offensive

While many offensive pokemon just go all out max attack or special attack, sometimes you only need your pokemon to 2HKO/OHKO a certain threat to your team. This is when a complex EV spread needs some but not maximum offensive investment. This is when the nugget bridge damage calculator comes in, just spam enough EVs in power to KO your specific threat 100% of the time because you don't want to rely on damage rolls. Make sure to account for damage boosting items, etc. For example when calculating enough EVs for a Politoed to 2HKO Kangaskhan with Scald, be sure to make sure that the rain booster is accounted for since it boosts the power by 50% which is a big deal.

[BC]Defensive

One the defensive side of things, players will EV a pokemon to take a certain attack from a certain threat to the team, or the pokemon itself, which then gives it an opportunity to use a move in return, or set up a move such as Trick Room. There are ways to improve bulk through items as well, such as a sitrus berry. A sitrus berry can make a 2HKO a 3HKO if EVd correctly, and it is great defensive booster. Specific berries such as the Colbur berry cut damage in half from just dark type moves. This can be nice for pokemon such as cresselia who are weak to it. There is a berry for every type as well. Don't EV to take a certain hit if it doesn't matter. For example, extensively cut an Arcanine's offensive power to its defenses just to survive blades when it can't do anything back. Sometimes in very specific situations its okay to beat combinations of pokemon, but most of the time it is not worth it.

[BC]Speed Creeping