DataBase Performance Issues with Indexes I'm reviewing a production database with over 400 tables and 658 indexes. I have determined that only 440 of these indexes are being used. Of these, many have fragmentation approaching 100% so I will be rebuilding and reorganizing them as needs require. Many reports are crawling, etc. 

One thing I noticed on querying the system views is that all indexes have a fill factor of 0. So my question is twofold: should I aim for a fill factor of 90% and monitor it, and should I adjust the fill factor BEFORE rebuilding indexes?
Fill factor will leave free space on your index pages. If you know that updates on index keys will need aditional space, then it may be ok to leave that 10% free. But if there will be no changes on index keys, it is better to have no free space on index (remember that all pages will generate logical reads on querys, so More pages = More logical reads = slower execution).

If you change fill factor, immediatly you will be asked to do rebuild