to get Latios or Latias in Ruby, Sapphire and Emerald you must first beat the Elite 4 and the champion. Then when you get home watch the TV your mother will ask if the Pokemon you saw on TV. was blue or red. If you say blue you get Latios but if you say red you get Latias. but you have to find them in the wild and they could be anywhere
From The lady inMT.PYRE
After you beat the Pokemon league, you go back to your house, and your mom asks you if you saw a report on TV. Then she asks you what color the Pokemon was, red or blue, and your answer determines which one you catch. Red is Latias and Blue is Latios. Then you walk around and randomly run into it and catch it with a master ball.
you make a dig and it will explofde and all will live happy
you can yous stones or if you have hacks you can yous 999 rear candys
just go to where you can find him, northeast of the map
when you get the sappphire, give it to the guy in island 1. if you get the ruby too and give it to the guy in the Pokemon center on island 1, you will find the cave to get Mewtwo. :)
Walk around the whole region and you'll find 'em.
Any HMS
A Weedle.
In Pokemon Leaf Green, you can catch Pokemon in the grass, water, or in a cave.
In Pokemon black you catch RESHIRAM and TORNADUS In Pokemon white you catch ZEKROM and THUNDERUS Sources : myself
you cannot catch the 3 regi's in Pokemon platinum you have to catch them in Pokemon emerald then transfer them to Pokemon platinum. thnx