* Shiny Rates: Shiny Pokemon in Pokemon Black have a very low chance of appearing - 1/4096. This means you'd have to encounter a *lot* of Pokemon before you'd be likely to find a shiny.
* No Shiny Charm: Unlike later games, Pokemon Black doesn't have a Shiny Charm item that increases your chances of finding shinies.
How people find Shiny Pokemon in Pokemon Black:
* Masuda Method: This is a breeding technique that involves breeding two Pokemon from different regions (for example, one from a Japanese game and one from an English game). This increases the shiny chance to 1/1365.
* Chain Fishing/Battling: The longer you chain battles or catches (without breaking the chain), the slightly higher your chances of finding a shiny become.
* Shiny Hunting Software: There are programs and apps that can help you find shinies, but this would be considered cheating.
Bottom Line: It's *very* difficult to find Shiny Pokemon in Pokemon Black without using external tools or the Masuda Method. Be prepared for a lot of patience!