Fire Red and Leaf Green will use the Generation 3 EV/IV formulas as that is the generation they were currently in when they released the game.
As for EV/IV training in general, check out this guide: Big Training Guide - EVs, IVs and Natures
Generation 3 IV Formulas
Since Generation III, effort points have been completely separate values from base stats. Defeated Pokémon give out 1, 2 or 3 effort points to a particular stat, depending on species (see list of Pokémon by effort value yield).
However, in battles that do not give any experience (such as in the Battle Tower or if the Pokémon is level 100, although the latter is no longer an issue in later generations), Pokémon will not gain any effort points. At level 100, a Pokémon's stats will be one stat point higher in a specific stat for every four effort points gained in that stat.
Pokémon are limited to a total of 255 effort points per stat, and 510 effort points in total. However, since stats are calculated by dividing effort by 4 and disregarding the remainder, only 252 effort points are required to maximize a stat. In Generation VI, the limit was changed from 255 to 252, preventing wasting EVs.
Vitamins add 10 effort points, but cannot raise a stat above 100, or raise the total above 510. These Vitamins can be found for 9,800 in Department Stores or in Laverre City in Generation VI.
For more information on EVs and IVs check out Bulbapedia or simply Google Pokemon Effort Values or Pokemon Individual Values and I'm sure you'll find the information and guides you're looking for.