Script to find out the Missing Indexes in Database :

DECLARE @dbid INT

SELECT @dbid = Db_id('database_name')

SELECT d.statement                     AS table_with_missing_index,
       s.avg_user_impact,
       CONVERT(INT, ( unique_compiles + user_seeks + user_scans ) *
                    avg_total_user_cost
                    * (
                    avg_user_impact )) AS index_advantage,
       d.equality_columns,
       d.inequality_columns,
       d.included_columns,
       s.avg_total_user_cost,
       s.unique_compiles,
       s.user_seeks,
       s.user_scans,
       s.last_user_seek
FROM   sys.dm_db_missing_index_group_stats s,
       sys.dm_db_missing_index_groups g,
       sys.dm_db_missing_index_details d
WHERE  s.group_handle = g.index_group_handle
       AND d.index_handle = g.index_handle
       AND database_id = @dbid
ORDER  BY d.statement,
          index_advantage DESC,
          s.avg_user_impact DESC