Where do you get latios in pokemon emerald?

Answer 1

After you beat the Elite 4 in Emerald, you'll wind up back at your house. Go downstairs and your mom will tell you to look at the TV

It will say something about a BZZZTTT colored Pokemon flying around Hoenn

Your mom will ask what color you think the Pokemon is.

if you want Latias, choose RED

if you want Latios, choose BLUE

You can get the other with an Eon ticket given out at a Nintendo Pokemon convention, whenever that will be.

Stock up on Ultra Balls, and preferably get a Pokemon that knows False Swipe, which always leaves 1 HP left. Also get a status inflicting Pokemon, that knows something that will put it sleep or paralyze it. Do not burn or poison it.

Get those, and go traveling around Hoenn. since I think it appears randomly, but only once. Save very often. If you accidently kill it, or it runs away, restart the game.

If it helps, I found it around Mossdeep.