How to catch Latias/Latios easily.
There are two ways you can do this. One is easy, while the other is a bit more difficult. Let's start with the more difficult one first.
First thing you are going to need is a Wobbuffet at a decent level (40 or so). It's special Ability is Shadow Tag, which prevents the foe from escaping or switching out. Just what we need.
Purchase a decent amount of Ultra Balls. Some Hyper Potions won't hurt either, even though Wobbuffet won't take much damage from Latias/Latios.
Run around and find this sucker. Make sure that Wobbuffet is first in your party (obviously) and be prepared for Latias/Latios to appear at any time.
When it appears, start chucking Ultra Balls at it. Wobbuffet's Shadow Tag keeps them from fleeing from battle. Use any Potions if you need to. Repeat until you have captured this beast.
Now for the easier way. First thing you are going to need is a speedy Pokemon that knows the move Mean Look, such as Crobat. Mean Look has the same effect as Wobbuffet's Shadow Tag, so you can probably guess why we're going to need it.
Have a decent number of Ultra Balls, and also a Pokemon to weaken Latias/Latios with you.
Run around and find this thing, with Crobat out front. As soon as you enter battle, use Mean Look. You are now free to start using Ultra Balls! I would suggest, however, that you switch to your attacking Pokemon and lower Latias/Latios's health to make it easier to capture it. Repeat until you have captured it.
Added by: Green_Fire Apr 6th 2010, ID#13031