You have to do the following things while you are involving in Data Load testing.

1. You have know about source data (table(s), columns, datatypes and Contraints)

2. You have to know about Target data (table(s), columns, datatypes and Contraints)

3. You have to check the compatibility of Source and Target.

4. You have to Open corresponding DTS package in SQL Enterprise Manager and run the DTS package (If you are using SQL Server).

5. Then you should compare the column's data of Source and Target.

6. You have to check the number to rows of Source and Target.

7. Then you have to update the data in Source and see the change is reflecting in Target or not.

8. You have to check about junk character and NULLs.