I focus on natures, IVs, and EVs when raising my Pokemon. Since I've got my Diamond version back in April 2007, my basic standard goes as follows.
The natures that I use would hinder either Attack or SP ATK (Adamant, Jolly, Modest, Timid, Impish, Careful, Bold, Calm).
Regarding IVs, I try to at least get three stats that I'm EV training to have at least a range of 20-31, maybe even 25-31.
For EVs, sweepers would usually have EVs for HP, Attack / SP ATK, and Speed. Walls would have EVs for HP, Defense, and SP DEF. Tanks would have EVs for HP, Attack / SP ATK, and Defense / SP DEF.