Fly around from place to place and hope to god you find them. Avoid using Pokemon much stronger than them because if they die they don't come back. If you have a Pokemon that can use False Swipe, use it. It deals damage but never kills a Pokemon, only brings them as close as 1 hp. Or just masterball.
no.
Only by trading them from Gold, Silver or Crystal.
check it out on your pokegear map
yes you can also catch them in soul silver.
The three legendary birds (articuno, zapdos, and moltres) cannot be found in Pokemon silver. They must be traded from Pokemon red, blue, or yellow.
Moltres is the only legendary Pokemon in Mt. Silver for HeartGold / SoulSilver only.
You can find Lugia, the legendary dogs/ Suicune, Enti, and Raichu, and I think Ho-Ho
7 "legendary" Pokemon
The Legendary is Lugia it can be found in whirl islands
Moltas: the fire legendary bird Pokemon the second strongest bird Pokemon
moltress
the only legendary that you can breed is manaphy. and that will result in a phione.