Do not automatically create all the indexes that the missing index DMVs suggest, that's a good way to severely over-index and hinder performance.
Evaluate what the missing index DMVs suggest, examine the existing indexes, test the suggestions, implement what's useful.
Gail Shaw
Microsoft Certified Master: SQL Server, MVP, M.Sc (Comp Sci)
SQL In The Wild: Discussions on DB performance with occasional diversions into recoverability