On Gold and Silver, all 3 dogs run around Johto and only Johto (you don't want to search Kanto as well would you?) When you run in to one, it will be lvl:40 and book it when they get the chance. All 3 know Roar so Mean Look won't be as useful. What I like to do is let them run around Johto until I get the Master Ball. Then I duplicate it so I have 5 (I use the Master Balls on the Legendaries so I don't have to sit for hours and hours on end trying to catch them.) Then I go catch them.
As for Crystal Version, you should know that you battle Suicune in the Tin Tower and it knows: Bubblebeam, Leer, Gust, and Rain Dance. It doesn't run so you catch it like the other Legends. Raikou and Entei still run around Johto, so follow what I said in the Gold and Silver half. The best way to tell if you ran into a dog on Crystal is the battle music will be very different.
What I think you are asking is how to find them. I just run into them unintentionally, then look for them when I get the chance. They don't have a set location, so check their area in the Poke'dex to locate the dogs you have seen.
I hope this cleared things up a little 4 ya. I still need to find
on my Gold.
hahahah