I've never had to do this, so I may not have the whole answer. But at least to start with, you need to use column datatypes that can store international characters. For example, instead of char() and varchar(), you will be using nchar() and nvarchar(). These datatypes can store non-English characters, but to do so they consume two bytes per character instead of just one.
Also, read these topics in BooksOnLine:
- SQL Language Support
- Unicode Data
- Using Unicode Data