Review missing index findings before you implement
There are a number of queries widely available that will look at the DMVs and tell you what indexes you may be missing. This is a great help with performance tuning your SQL Server. But be cautious of what you implement. You should not just go and create all of these indexes without first reviewing existing indexes on the tables affected. Some of the missing index queries results may have indexes that have a large amount of included columns (maybe all the columns in the table). The results may also include indexes that already exist, either partially or fully and you don't want to create duplicate indexes. So use the queries, but examine the results of each new index recommendation before you go and create the new indexes. Also use the helpindex stored procedures (that I have blogged about previously). After you have done this test your new indexes (maybe just add one index at a time), they may help some queries - but may not be so good on others. Always have a drop index script at the ready (just in case things go pear shaped).