Use DBCC CHECKDB. Preferably before the backup too. If after the restore, DBCC CHECKDB returns consistency errors, you can at least tell if the error was because the database was inconsistent to start with, or because the backup file was damaged between the time of backup and restore. Without a DBCC CHECKDB before the backup, you can't tell.

Or if using SQL 2005 or later, using the CHECKSUM option during the backup process will also cause SQL Server to verify page checksums where present. Not as informative as DBCC CHECKDB, but still checks the consistency of your data.