The basic idea of both IVs and EVs is the same in R/S/E as in the modern games: IVs are set when you encounter the Pokémon and can't be changed, bred Pokémon inherit three IVs from their parents, effort points are gained whenever a Pokémon gets experience for the defeat of another Pokémon according to that Pokémon's effort yield, no EV can be higher than 255, and you can't have more than 510 effort points total.
However, a number of convenience features introduced in later games are not available. There is no Destiny Knot or power items to make IV breeding easier and no automatic perfect IVs for special Pokémon. There is no characteristic on the stat screen indicating the Pokémon's highest IV. There is no way to remove effort points after they've been gained, unless you're playing Emerald in which Pomeg, Kelpsy, Qualot, Hondew, Grepa and Tamato berries remove ten effort points from HP, Attack, Defense, Special Attack, Special Defense and Speed respectively. There is no Super Training to let you raise your Pokémon's EVs without battling, only vitamins (and you can't use vitamins on a Pokémon with more than 100 effort points in that stat).
So depending on exactly what modern methods you were thinking of, they may or may not apply. In general everything is a lot harder in R/S/E, especially R/S where any effort points your Pokémon gained were stuck on them forever with no chance of starting over. The core idea is still the same, however.
