As with any Pokemon, you need to only bring its health down and use appropriate Pokeballs. It will disappear if defeated, however, a common misconception is that once any legendary Pokemon in Black/White is defeated then it can't be caught again. If it has run away, fear not. If it's the first play-through of the game then you'll have to wait until you can challenge the Elite Four and catch Zekrom/Reshiram until you can battle any of the legendary Pokemon again (if they haven't already been caught).
However, should anyone accidentally defeat Virizion, Kyurem, Terrakion or Cobalion and save afterwards, then all you have to do is beat the Elite Four and Alder, the League Champion again. Your game will save and you'll be back at your house from the beginning. From here, simply travel back to Rumination Field via Pinwheel Forest and it will be back again.
Hopefully this clears up any doubts about defeating Legendary Pokemon instead of catching them.
beat the Pokemon league
You can catch the main white legendary, Kyrugem, Virizion, Cobalion, Terrakion, Thunderous, Victini, Zorua, Zoroark, Volcarona, and Landorus.
acually there is but not Reshiram or Zecrom but you can get cobalion terrakion and virizion
After you beat the elite four and the galactic biulding
With a Mew you have to catch him with a Master Ball
You catch it in the Pinwheel Forest but only after you have caught Cobalion, which is at Mistralton cave ok, but what if you already beat it. then what do you do?
To even get to Virizion, you have to catch Cobalion in Mistralton Cave. Virizion, is in Pinwheel Forest.
In Pokemon White, you can find virizion in a clearing in pinwheel forest that isn't accessable untill you catch Cobalion.
you first have to catch/defeat the legendary pokemon cobalion in mistralion cave you catch virizion in pinwheel forest
It seems any legendaries you failed to catch will come back after you beat the Elite Four (if you've already done it, go beat them again).
First you have to catch Cobalion in the Challengers cave and then you go to Pinwheel Forest. In the east there is a passage to a small field and Virizion is there.
first you have to beat the Pokemon league, then you go to mistralton cave ( near driftveil city ) and catch cobalion. (YOU HAVE TO CATCH COBALION BEFORE YOU CAN GET VIRIZION). Then you go to pinwheel forest (near nacrene city) and you go through a gap between the fence and follow the path until you get to the rumination field. If there are boulders blocking the way you will have to go and catch terrikon first
Did you already catch Cobalion? it is impossible to catch virizion until you have caught cobalion. I'm not sure what happens if you faint it......so good luck
Yes, you need Cobalion to catch Virizion. You also need him to catch Terrakion in Victory Road. They are called something like the musket three but i forgot. You meet all of them at level 42.
You first have to catch Cobalion so you can then catch Virizion. Because when you go to pinweel forest there are some stones covering the path to Virizion so I'd recommend getting Cobalion first. Then after that you can catch Terrakion.
beat the Pokemon league
In Pinwheel Forest Rumination Field but, only after you catch Cobalion.