Hi How do you get shinny pokemon ! Thanks.?

It's random you have a 1/8192 chance of that Pokemon being shiny when encountered in the wild.

It might not work for you but it did work for me. One time, I dropped my GBA and the Emerald Cartridge fell out. I put it back in and turned the game on. The first Pokemon I found was a shiny Tentacool. I don't know if this is a secret or if i'm just lucky but I swear it worked for me.

The trick is to recognize them when you're faced with one, then make sure you catch it! A "shiny" will have different colors, but sometimes it's hard to tell. Also, it will have stars go around it when the battle begins, but it's really quick, so you might not see it if you're not looking closely. It's not very often that you'll bump into one. I have only 2-one blue-eyed Venonat caught over 250 hours into LeafGreen, and then a green spotted Spinda in Sapphire with fewer than 40 hours on it(I almost missed him cuz it was hard to tell at first).
Patience, you'll run into one sonner or later if you keep playing, and keep a Masterball handy if you can, because you don't want to run into one, then lose it! [Won't help in Safari Zone, though :( ]
BTW-the color/stars are the only differences, the poke will be normal in every other way, but they sure are cool!
Happy Shiny Hunting!
P.S. Some are obvious, some aren't, but if you check around this site, you'll read about what colors the shiny ones people have caught are, so you know what to look for.(Like a Shiny Charizard is black, a Shiny Psyduck is red or blue, I think, or some other obviously different color, etc.)