I have been hunting latias for about 2 days. Her health is in the low red..

I'll teach you my method-I catched her with it. Firstly, have a swellow that knows endeavor. Have it at level 40 or higher and equip it with the quick claw(found in the Pokemon school, rustboro) so that is speed is higher than latias's.

Then, you have to bring it's hp down to 1. You can do this by poisoning it, walking around with it and when it has only 1 hp left, use antidote.

You also must have a wobbufet(or wynaut) at a level as high as possible (so it can take a few attacks from latias). Put swellow first in your party Now, go to the weather institute and check if latias is in this route.

If not, go in the institute, back out, and check again. When she's in the route, go looking for her in the tall grass. When you encountered her, use endeavor.

Latias will now have only 1 hp. Search for her again, but this time, put wobbufet first. (so that she can't escape).

Encounter, and now, just keep using ultra balls(because of it's 1 hp, you won't even have to throw in a status problem)
I catched her from the first shot, but it might take a while.

And voila, you catched latias without having to use a masterball!!
Then, for the button-pressing: IT'S FALSE!!!

Sure, people say that it works, and the they"prove"it by fighting a low level Pokemon and do the trick. Yahoo, it works. But there is no possible way to do have a 100 % catch rate without a masterball.
Hope i've helped;)
Shadow Lugia

Exept in Pokemon Blue/Red/Yellow, there is such thing with an ultraball.

The method that I used for latias is a method with only one pok�mon and no master balls.

I found latias next to the weather institute, but I was allready prepared for a meeting with her. I used a Sableye of level 60 and I equipped the Quick Claw item on it. When the battle began, I auto-tagged in my Sableye because he was the first one in line. With his Quick Claw he could use Mean Look before Latias could escape. Then I used all other attacks as many times as possible to get her HP down. Then I threw a great ball and I had her after 3 tries!

In fact, the catch was a lucky shot. I forgot that the Psychic attacks of latias could kill my Sableye in one blow. Lucky for me, she kept using Water Sport and Wish. My Sableye was lucky to run into such a weak moves.

If you want to play safe, don't use my method. Only for use if you want a challenge....

Initially, I just saved after using a max repel in a patch of grass (any route should work) and soft reset if I didnt encounter her before the repel wore off (staying on the same route the entire time) each time you reset, she switches routes (just as Raikou, Entei, and Suicune did in GSC) by that logic, each time you reset, you have a 1/32 shot at nabbing an encounter. The first time I encounter a Lati, I tend to use it to document the location, and not actually do any damage, or inflict a status problem.

My strategy in SS/HG was to switch between 2 or 3 routes and keep checking my pokegear for Entei/Raikou, and use a Pokemon with Mean Look to trap them for a short time, and whittle down the HP, let them flee, and then equip a Scyther with False Swipe, and a Silk Scarf to enhance the power of it's false swipe, and hope for a critical hit. (I only pull Scyther out when the health is redbar)

Anyway, thats a way to do it. Its a bitlonger than most, but it achieves the same result.