How would you implement sequences in Microsoft SQL Server?

Sql Server 2012 has introduced SEQUENCE objects, which allow you to generate sequential numeric values not associated with any table.

Creating them are easy:

CREATE SEQUENCE Schema.SequenceName
AS int
INCREMENT BY 1 ;

An example of using them before insertion:

DECLARE @NextID int ;
SET @NextID = NEXT VALUE FOR Schema.SequenceName;
-- Some work happens
INSERT Schema.Orders (OrderID, Name, Qty)
  VALUES (@NextID, 'Rim', 2) ;

See my blog for an in-depth look at how to use sequences:

Sequences in SQL server 2012 – Implementing,Managing, Performance