This subject is very deep subject but today we will see it very quickly and most important points. May be following up on few of the points of this point will help users to right away improve the performance of query. In this article I am not focusing on in depth analysis of database but simple tricks which DBA can apply to gain immediate performance gain.
There are few hardware upgrades can be considered as well like separating index on different disk drive or moving tempdb to another drive. However, I am not suggesting them here as they are not quick way to improve the performance of query.
Reference : Pinal Dave (http://blog.SQLAuthority.com)