What's the best practice for handling unique identifiers in SQL Server?

The best practice is to rely on SQL Server's built-in identity columns for automatically generating unique identifiers whenever possible. If a globally unique identifier is absolutely required, use `NEWID()` with caution, considering performance implications. For scenarios requiring sequential identifiers within a single instance, `NEWSEQUENTIALID()` can be a more efficient choice. Avoid using user-defined functions or computed columns directly to populate identity columns.