This is the SQL statement I use to find what % of index are fragmented.
SELECT A.object_id
, A.index_id
, [name]
, Avg_Fragmentation_In_Percent
FROM sys.dm_db_index_physical_stats (db_id(), NULL,NULL, NULL, NULL) AS A
JOIN sys.indexes B WITH(NOLOCK)
ON A.Object_id = B.Object_id
AND A.Index_id = B.Index_id
WHERE [name] IS NOT NULL
If Avg_Fragmentation_In_Percent is > 5% and <= 30%; ALTER INDEX REORGANIZE.
If Avg_Fragmentation_In_Percent is > 30%; ALTER INDEX REBUILD WITH (ONLINE = ON)*.
* Rebuilding an index can be executed online or offline. Reorganizing an index is always executed online. To achieve availability similar to the reorganize option, you should rebuild indexes online (SQL BOL).