You can only get latias if you have the mational dex.
Find the hidden stairs in your Pokemon in-game house go down them and latias and latios will be there.
anime4everpink- I didn't have the national dex and still found one. Ugh this brings back memories DX I almost caught it too. I forgot the name of the town/city But it's where the fortree gym is, and it rains frequently. I found it while Surfing. I've been told they can appear anywhere. Always be ready, Latios and Latias can flee from battle, and it only appears once in the game. I recommend a Pokemon with the move glare, and/or with an ability, attack, or item that prevents fleeing. If you would rather have this Pokemon that Kyogure, use your masterball.
There is no secret or hidden trick to finding Latias or Latios. Well you can use a Action Replay or a Game Shark but I'm talking about not cheating. You find him randomly. I was playing Saphire trying to Find the Regi Pokemon while I was surfing, and i got into a wild Pokemon battle with Latias without even trying to find him. So the best way to find him is to not try to find him.
The only possible way to obtain Latias in Fire Red/Leaf Green, is to trade from Ruby/Saphire/Emerald
Latios isn't in Pokémon Sapphire, but Latias is. Latias is in Pokémon Ruby! However, you can trade Latios from Pokémon Ruby to get it.
Ruby and Saphire vary in available Pokémon, a little bit on storyline, and by the tent color that you get from the Trick Master between Slateport City and Mauville City. You can catch Latios, Lunatone, and Kyogre in Saphire. You can find Latias, Solrock, and Groudon in Ruby.
Either trade them from Pokemon ruby and sapire or beat the elite 4 and watch the tv and say red for latias or blue for latios then get the eon ticket to get the other one. Mix Records with Ruby or Saphire to get the eon ticket
You can find Latias and latios anywhere in Hoenn. You just have to get lucky.
You can find Latias in Soulsilver throughout the Kanto region.
You can find latias on every route in hoenn.
Latias is not available in SoulSilver
You find latias by first going to the TV at your house in littleroot town after you've beaten the elite four. The TV will say there was reports of something flying in the sky, and your mom will ask you what color it was. ( Say red for latias, blue for latios). Next, buy some max repels, put a level 30 Pokemon at the front of your party, put apokemon with sweet scent in your party, and go to a very grassy area. If you use a max repel and sweet scent, you should be able to get you lati! (Note: you must have a master ball to catch lati.)If you wish to find a Latias or Latios you have to migrate them from one of the three GBA saphire, Emerald, or Ruby.
In the Cave of Origin.
you have to find all the ompa lompas