Export a SQL Server 2000 database to Server 2012
Since your source server is SQL Server 2000, you can't restore directly to SQL Server 2012. You will need to restore to another instance first (2005, 2008, or 2008 R2).

On 2000:

BACKUP DATABASE dbname TO DISK = 'D:\backups\db.bak' WITH INIT;


On 2005 or 2008 or 2008 R2:

RESTORE DATABASE dbname FROM DISK = 'D:\restores\db.bak'
  WITH REPLACE, RECOVERY, MOVE (...you will likely have to specify new file locations...);


Then from there, back it up again, and then restore on the 2012 server.

Once you've restored, you'll probably want to adjust the compatibility level:

ALTER DATABASE dbname SET COMPATIBILITY_LEVEL = 110;


As well as update statistics. But note that 80 compatibility will automatically be upgraded to 90 (and you will have issues if you use syntax that is no longer supported, e.g. *= joins). While it won't catch everything, you may want to run the 2012 Upgrade Advisor while the database is in its temporary home on a 2005, 2008 or 2008 R2 instance to catch any potential issues. Also see this answer for ways the change in compatibility level may affect your existing code (the upgrade advisor won't catch many of those).