Probably a Master Ball if you've got one, because they can run away at any time.
If you don't have enigma stone, keep it for Latios is my advice
yes unless you have a master ball latios is hard to catch
Latios, since rayquaza does not run away.
timerball
Master Ball.
Yes
If you have already beaten the elite four and have Latios or Latias already roming around in emerald then you can chase it down till you are in the same vicinity as it and go into the grass to see it appear. toss a master ball at it and you will have the latios or latias. Of course it's best that you clone the master ball first so that you can catch the other one the same way.
any ball just depends on how you weaken it and how lucky you are
latios's sole is in the crytal ball just like his father's sole was becus he saved the world.
yes but it is hard and you have to be lucky
In Pokemon ruby you can catch latios but not latias, in Pokemon sapphire you can catch latias not latios, in emerald you can choose. Use your master balls on them so they wont fly away. You can use other types of balls, eg timer ball, ultra ball, or great ball on the other legendaries.
It is best to get rayquaza. Use mean look on latias and latios, it'll stop them fleaing.