Check http://sqlserverperformance.wordpress.com/2011/02/04/five-dmv-queries-that-will-make-you-a-superhero-in-2011/

>I have an index which is defined with a combination of three fields. Usually, for big queries which take a few seconds, we usually create those type of indexes in respect to the where clause of the SQL command in the same order in the index field order definition.
>
>When I look at the execution plan, I can now see that it uses this index and this simplifies the execution plan. When I move the mouse over the specific object in the execution plan, I can see that there is an output list. Is this the recommanded include fields I should also add in this index?