This is entirely too vague for anything resembling a cohesive response. What you are asking is a very big topic. I would suggest you start reading up on indexes in depth so you better understand how they work. Once you have that knowledge you will know what types of indexes would be appropriate in the situations you are asking about. Lucky for you there is a spectacular series of articles right here on SSC that discusses indexes from the basics to a pretty deep level. http://www.sqlservercentral.com/stairway/72399/