Choose The Appropriate Cluster Index

You get exactly one clustered index on a table. Ensure you have it in the right place. First choice is the most frequently accessed column, which may or may not be the primary key. Second choice is a column that structures the storage in a way that helps performance. This is a must for partitioning data.

Furthermore, clustered index are always sorted on disk. To avoid fragmentation, you should put it on a sequential value if possible. For example, putting on a MD5 will create lots of fragments especially if there is lots of insert in the table.

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