5) Check for any table or Index scans. Using the execution plan, it's easy to identify if the SQL statement is performing any table or index scans. In the majority of cases (assuming that statistics are up to date), this indicates that an index is missing. These three DMVs might prove useful to identify missing indexes:
This should be reworded to Check for any table or Clustered Index Scans. Regular non-clustered index scans can happen for many other reasons, including pulling a wide enough range of data from the table that an index scan is warranted, somebody using a non-deterministic function in a where clause, etc.
Creating a new index in an attempt to cover an index that an existing index scan is likely serving won't necessarily generate an index seek afterwards.