To be honest, the most accurate is to tune by hand, look at problematic queries, create indexes to support them. DTA's OK if you don't know how enough about indexes to choose good ones yourself, but you do have to test all its recommendations before implementing them.
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