SQL Server bulk insert performance
Below are some good ways to improve BULK INSERT operations :


Using TABLOCK as query hint.
Dropping Indexes during Bulk Load operation and then once it is completed then recreating them.
Changing the Recovery model of database to be BULK_LOGGED during the load operation.
If the target has Clustered Index then specifying ORDER BY clause in the bulk insert operation will increase the speed of BULK loading.
Using Trace Flag 610 at the beginning of BULK INSERT operation.


The max degree of parallelism should be configured on the server rather than the default. You can refer to my answer on how it configure it here.

Some good reference with interesting stats are given in The Data Loading Performance Guide here
. Have a Look at BATCHSIZE and ROWS_PER_BATCH as well in the guide.